Antireflective film and display device

ABSTRACT

An object of the present invention is to provide an antireflective film having an anti-reflection function with which reflection of incident light from external can be further reduced and a high-visibility display device having such an antireflective film. The tops of the plurality of pyramidal projections are evenly spaced and each side of the base of a pyramidal projection is in contact with one side of the base of an adjacent pyramidal projection. That is, one pyramidal projection is surrounded by other pyramidal projections, and the base of the pyramidal projection and the base of the adjacent pyramidal projection have a side in common.

TECHNICAL FIELD

The present invention relates to an antireflective film having ananti-reflection function and a display device having the antireflectivefilm.

BACKGROUND ART

As to some display devices having various displays (such as a liquidcrystal display and an electroluminescent display (hereinafter alsoreferred to as an EL display)), there may be a case where it becomesdifficult to see a display screen due to reflection of its surroundingsby surface reflection of incident light from external and thusvisibility is decreased. This is a particularly significant problem whena display device grows in size or is used outside.

In order to prevent such reflection of incident light from external, amethod of providing an antireflective film over a display screen surfaceof a display device has been employed. For example, there is a method ofproviding a multilayer structure of stacked layers having differentrefractive indices for an antireflective film so that the antireflectivefilm is effective for a wide visible light wavelength range (see, forexample, Patent Document 1: Japanese Published Patent Application No.2003-248102). With a multilayer structure, incident light from externalreflected at each interface between the stacked layers interfere andcancel each other, which provides an anti-reflection effect.

As to an antireflective structure, fine conical or pyramidal projectionsare arranged over a substrate to reduce reflectance of light on asurface of the substrate (for example, see Patent Document 2: JapanesePublished Patent Application No. 2004-85831).

DISCLOSURE OF INVENTION

However, with the above-described multilayer structure, a light beam,which cannot be cancelled, of the incident light from external reflectedat each layer interface is emitted to the viewer side as reflectedlight. In order to achieve mutual cancellation of incident light fromexternal, it is necessary to precisely control optical characteristicsof materials, thicknesses, and the like of films to be stacked, and ithas been difficult to perform anti-reflection treatment on all incidentlight from external which are incident from various angles. Further ananti-reflection function of a conical or pyramidal antireflectivestructure has been not enough.

In view of the foregoing, a conventional antireflective film has afunctional limitation, and an antireflective film having a higheranti-reflection function, and a display device having such ananti-reflection function have been demanded.

It is an object of the present invention to provide a high-visibilitydisplay device with an anti-reflection function with which reflection oflight from external can be further reduced, and a method formanufacturing such a display device.

According to the present invention, since the plurality of pyramidalprojections are densely arranged with no space therebetween, arefractive index varies from the display screen surface side to theoutside (the air) due to the physical shape of a pyramidal projection.In the present invention, the tops of the plurality of pyramidalprojections are evenly spaced and each side of the base of a pyramidalprojection is in contact with one side of the base of an adjacentpyramidal projection. That is, one pyramidal projection is surrounded byother pyramidal projections, and the base of the pyramidal projectionand the base of the adjacent pyramidal projection have a side in common.

Thus, since the pyramidal projections are densely arranged so that thetops thereof are evenly spaced, the antireflective film has a highanti-reflection function with which incident light can be efficientlyscattered in many directions.

In the present invention, the distance between the tops of the pluralityof pyramidal projections is preferably equal to or shorter than 350 nm,and the height of each of the plurality of pyramidal projections ispreferably equal to or longer than 800 nm. The fill rate of bases of theplurality of pyramidal projections per unit area of a display screen(the rate of the display screen which is filled (occupied)) is equal toor more than 80%, preferably equal to or more than 90%. A fill rate is arate of a formation region of pyramidal projections over a displayscreen surface. When the fill rate is equal to or more than 80%, therate of plane portions where no pyramidal projection is formed (which isparallel to the display screen) is equal to or less than 20%. The ratioof the height of a pyramidal projection to the width of a base thereofis equal to or more than 5.

According to the present invention, an antireflective film (substrate)and a display device having a plurality of pyramidal projections whichare adjacent to each other can be provided, and a high anti-reflectionfunction can be provided.

The present invention can also be applied to a display device that is adevice having a display function. A display device using the presentinvention may be a light-emitting display device in which alight-emitting element including a layer containing an organic material,an inorganic material, or a mixture of an organic material and aninorganic material which produces light emission calledelectroluminescence (hereinafter also referred to as EL) betweenelectrodes is connected to a TFT; a liquid crystal display device usinga liquid crystal element containing a liquid crystal material as adisplay element; or the like. In the present invention, a display devicecorresponds to a device including a display element (a liquid crystalelement, a light-emitting element, or the like). It is to be noted thata display device may be a main body of a display panel in which aplurality of pixels including display elements such as liquid crystalelements or EL elements and a peripheral driver circuits for driving thepixels are formed over a substrate. Further, a display device may be theone provided with a flexible printed circuit (FPC) or a printed wiringboard (PWB) which includes one or more of an IC, a resistor, acapacitor, an inductor, a transistor, and the like. Moreover, a displaydevice may include an optical sheet such as a polarizing plate or aretardation film. In addition, a backlight (such as a light guide plate,a prism sheet, a diffusion sheet, a reflection sheet, a light source (anLED, a cold-cathode tube, or the like)) may be included.

Note that various modes can be applied to a display element and adisplay device, and they can have various elements. For example, adisplay medium in which contrast is changed by an electromagnetic effectcan be used, such as an EL element (for example, an organic EL element,an inorganic EL element, an EL element containing an organic materialand an inorganic material), an electron discharging element, a liquidcrystal element, an electron ink, a grating light valve (GLV), a plasmadisplay (PDP), a digital micromirror device (DMD), a piezoelectricceramic display, or a carbon nanotube. It is to be noted that a displaydevice using an EL element may be an EL display; a display device usingan electron discharging element may be a field emission display (FED),an SED type flat panel display (Surface-conduction Electron-emitterDisplay), or the like; a display device using a liquid crystal elementmay be a liquid crystal display, a transmissive liquid crystal display,a semi-transmissive liquid crystal display, or a reflective liquidcrystal display; and a display device using an electron ink may beelectronic paper.

One mode of the antireflective film of the present invention has aplurality of pyramidal projections, wherein tops of the plurality ofpyramidal projections are evenly spaced, and each side of the base ofone pyramidal projection is in contact with one side of the base of anadjacent pyramidal projection.

Another mode of the antireflective film of the present invention has aplurality of pyramidal projections, wherein tops of the plurality ofpyramidal projections are evenly spaced, six adjacent pyramidalprojections are arranged around one pyramidal projection, and each sideof the base of one pyramidal projection is in contact with one side ofthe base of an adjacent pyramidal projection.

Another mode of the antireflective film of the present invention has aplurality of pyramidal projections, wherein tops of the plurality ofpyramidal projections are evenly spaced, each side of the base of onepyramidal projection is in contact with one side of the base of anadjacent pyramidal projection, the distance between the tops of theplurality of pyramidal projections is equal to or shorter than 350 nm,and the height of each of the plurality of pyramidal projections isequal to or longer than 800 nm.

Another mode of the antireflective film of the present invention has aplurality of pyramidal projections, wherein tops of the plurality ofpyramidal projections are evenly spaced, six adjacent pyramidalprojections are arranged around one pyramidal projection, each side ofthe base of one pyramidal projection is in contact with one side of thebase of an adjacent pyramidal projection, the distance between the topsof the plurality of pyramidal projections is equal to or shorter than350 nm, and the height of each of the plurality of pyramidal projectionsis equal to or longer than 800 nm.

Another mode of the antireflective film of the present invention has aplurality of pyramidal projections, wherein tops of the plurality ofpyramidal projections are evenly spaced, each side of the base of onepyramidal projection is in contact with one side of the base of anadjacent pyramidal projection, the distance between the tops of theplurality of pyramidal projections is equal to or shorter than 350 nm,the height of each of the plurality of pyramidal projections is equal toor longer than 800 nm, and the fill rate of bases of the plurality ofpyramidal projections per unit area is equal to or more than 80%.

Another mode of the antireflective film of the present invention has aplurality of pyramidal projections, wherein tops of the plurality ofpyramidal projections are evenly spaced, six adjacent pyramidalprojections are arranged around one pyramidal projection, each side ofthe base of one pyramidal projection is in contact with one side of thebase of an adjacent pyramidal projection, the distance between the topsof the plurality of pyramidal projections is equal to or shorter than350 nm, the height of each of the plurality of pyramidal projections isequal to or longer than 800 nm, and the fill rate of bases of theplurality of pyramidal projections per unit area is equal to or morethan 80%.

Another mode of the antireflective film of the present invention has aplurality of pyramidal projections, wherein tops of the plurality ofpyramidal projections are evenly spaced, each side of the base of onepyramidal projection is in contact with one side of the base of anadjacent pyramidal projection, the distance between the tops of theplurality of pyramidal projections is equal to or shorter than 350 nm,the height of each of the plurality of pyramidal projections is equal toor longer than 800 nm, the fill rate of bases of the plurality ofpyramidal projections per unit area is equal to or more than 80%, andthe ratio of the height of a pyramidal projection to the width of a basethereof is equal to or more than 5.

Another mode of the antireflective film of the present invention has aplurality of pyramidal projections, wherein tops of the plurality ofpyramidal projections are evenly spaced, six adjacent pyramidalprojections are arranged around one pyramidal projection, each side ofthe base of one pyramidal projection is in contact with one side of thebase of an adjacent pyramidal projection, the distance between the topsof the plurality of pyramidal projections is equal to or shorter than350 nm, the height of each of the plurality of pyramidal projections isequal to or longer than 800 nm, the fill rate of bases of the pluralityof pyramidal projections per unit area is equal to or more than 80%, andthe ratio of the height of a pyramidal projection to the width of a basethereof is equal to or more than 5.

One mode of the display device of the present invention includes a pairof substrates at least one of which is a light-transmitting substrate, adisplay element provided between the pair of substrates, and a pluralityof pyramidal projections on an outer side of the light-transmittingsubstrate, wherein tops of the plurality of pyramidal projections areevenly spaced, and each side of the base of one pyramidal projection isin contact with one side of the base of an adjacent pyramidalprojection.

Another mode of the display device of the present invention includes apair of substrates at least one of which is a light-transmittingsubstrate, a display element provided between the pair of substrates,and a plurality of pyramidal projections on an outer side of thelight-transmitting substrate, wherein tops of the plurality of pyramidalprojections are evenly spaced, six adjacent pyramidal projections arearranged around one pyramidal projection, and each side of the base ofone pyramidal projection is in contact with one side of the base of anadjacent pyramidal projection.

Another mode of the display device of the present invention includes apair of substrates at least one of which is a light-transmittingsubstrate, a display element provided between the pair of substrates,and a plurality of pyramidal projections on an outer side of thelight-transmitting substrate, wherein tops of the plurality of pyramidalprojections are evenly spaced, each side of the base of one pyramidalprojection is in contact with one side of the base of an adjacentpyramidal projection, the distance between the tops of the plurality ofpyramidal projections is equal to or shorter than 350 nm, and the heightof each of the plurality of pyramidal projections is equal to or longerthan 800 nm.

Another mode of the display device of the present invention includes apair of substrates at least one of which is a light-transmittingsubstrate, a display element provided between the pair of substrates,and a plurality of pyramidal projections on an outer side of thelight-transmitting substrate, wherein tops of the plurality of pyramidalprojections are evenly spaced, six adjacent pyramidal projections arearranged around one pyramidal projection, each side of the base of onepyramidal projection is in contact with one side of the base of anadjacent pyramidal projection, the distance between the tops of theplurality of pyramidal projections is equal to or shorter than 350 nm,and the height of each of the plurality of pyramidal projections isequal to or longer than 800 nm.

Another mode of the display device of the present invention includes apair of substrates at least one of which is a light-transmittingsubstrate, a display element provided between the pair of substrates,and a plurality of pyramidal projections on an outer side of thelight-transmitting substrate, wherein tops of the plurality of pyramidalprojections are evenly spaced, each side of the base of one pyramidalprojection is in contact with one side of the base of an adjacentpyramidal projection, the distance between the tops of the plurality ofpyramidal projections is equal to or shorter than 350 nm, the height ofeach of the plurality of pyramidal projections is equal to or longerthan 800 nm, and the fill rate of bases of the plurality of pyramidalprojections per unit area is equal to or more than 80%.

Another mode of the display device of the present invention includes apair of substrates at least one of which is a light-transmittingsubstrate, a display element provided between the pair of substrates,and a plurality of pyramidal projections on an outer side of thelight-transmitting substrate, wherein tops of the plurality of pyramidalprojections are evenly spaced, six adjacent pyramidal projections arearranged around one pyramidal projection, each side of the base of onepyramidal projection is in contact with one side of the base of anadjacent pyramidal projection, the distance between the tops of theplurality of pyramidal projections is equal to or shorter than 350 nm,the height of each of the plurality of pyramidal projections is equal toor longer than 800 nm, and the fill rate of bases of the plurality ofpyramidal projections per unit area is equal to or more than 80%.

Another mode of the display device of the present invention includes apair of substrates at least one of which is a light-transmittingsubstrate, a display element provided between the pair of substrates,and a plurality of pyramidal projections on an outer side of thelight-transmitting substrate, wherein tops of the plurality of pyramidalprojections are evenly spaced, each side of the base of one pyramidalprojection is in contact with one side of the base of an adjacentpyramidal projection, the distance between the tops of the plurality ofpyramidal projections is equal to or shorter than 350 nm, the height ofeach of the plurality of pyramidal projections is equal to or longerthan 800 nm, the fill rate of bases of the plurality of pyramidalprojections per unit area is equal to or more than 80%, and the ratio ofthe height of a pyramidal projection to the width of a base thereof isequal to or more than 5.

Another mode of the display device of the present invention includes apair of substrates at least one of which is a light-transmittingsubstrate, a display element provided between the pair of substrates,and a plurality of pyramidal projections on an outer side of thelight-transmitting substrate, wherein tops of the plurality of pyramidalprojections are evenly spaced, six adjacent pyramidal projections arearranged around one pyramidal projection, each side of the base of onepyramidal projection is in contact with one side of the base of anadjacent pyramidal projection, the distance between the tops of theplurality of pyramidal projections is equal to or shorter than 350 nm,the height of each of the plurality of pyramidal projections is equal toor longer than 800 nm, the fill rate of bases of the plurality ofpyramidal projections per unit area is equal to or more than 80%, andthe ratio of the height of a pyramidal projection to the width of a basethereof is equal to or more than 5.

The pyramidal projection can be formed of a material having a refractiveindex which is nonuniform and varies from the side surface toward adisplay screen. For example, in each of the plurality of pyramidalprojections, a portion closer to the side surface is formed of amaterial having a refractive index equivalent to that of the air toreduce reflection, by the side surface of the pyramidal projection, oflight incident on each pyramidal projection from external through theair. On the other hand, a portion of each of the plurality of pyramidalprojections, which is closer to the substrate on the display screenside, is formed of a material having a refractive index equivalent tothat of the substrate to further reduce reflection by an interfacebetween each pyramidal projection and the substrate, of incident lightfrom external which propagates inside each pyramidal projection and isincident on the substrate.

Since the refractive index of air is smaller than that of a glasssubstrate, when a glass substrate is used as the substrate, eachpyramidal projection may have such a structure in which a portion closerto the top of the pyramidal projection is formed of a material having alower refractive index and a portion closer to the base of the pyramidalprojection is formed of a material having a higher refractive index, sothat the refractive index increases from the top to the base of thepyramidal projection. When glass is used for the substrate, eachpyramidal projection can be formed of a film containing fluoride, oxide,or nitride.

The antireflective film and the display device of the present inventioninclude a plurality of pyramidal projections densely arranged with nospace therebetween on the surfaces of the antireflective film and thedisplay device. Reflected incident light from external is reflected tonot the viewer side but another adjacent pyramidal projection because aside surface of each pyramidal projection is not parallel to the displayscreen. Alternatively, reflected incident light propagates between thepyramidal projections. The pyramidal projections have shapes capable ofbeing densely arranged with no space therebetween, which are optimalshapes each having the largest number of sides among pyramidalprojections capable of being densely arranged with no space therebetweenand a high anti-reflection function with which light can be scatteredefficiently in many directions. Incident light from external is partlytransmitted through a pyramidal projection, and the rest of the incidentlight from external, which is reflected light, is then incident on anadjacent pyramidal projection. In this manner, the incident light fromexternal which is reflected by a side surface of the pyramidalprojection repeats incidence on adjacent pyramidal projections.

That is, the number of times that incident light from external isincident on the pyramidal projections of the antireflective film, of theincident light from external which is incident on the antireflectivefilm, is increased; therefore, the amount of light transmitted throughthe antireflective film is increased. Thus, the amount of light fromexternal reflected to the viewer side is reduced, and the cause of areduction in visibility such as reflection can be prevented.

The present invention can provide an antireflective film having ananti-reflection function with which reflection of incident light fromexternal can be further reduced by being provided with a plurality ofpyramidal projections on their surface, and a high-visibility displaydevice having such an antireflective film. Accordingly, a morehigh-quality and high-performance display device can be manufactured.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1D are schematic views of the present invention.

FIGS. 2A and 2B are schematic views of the present invention.

FIGS. 3A and 3B are schematic views of the present invention.

FIG. 4 is a cross-sectional view showing a display device of the presentinvention.

FIGS. 5A to 5C are a top plan view and cross-sectional views each ofwhich shows a display device of the present invention.

FIGS. 6A and 6B are cross-sectional views each showing a display deviceof the present invention.

FIGS. 7A and 7B are cross-sectional views each showing a display deviceof the present invention.

FIGS. 8A and 8B are a top plan view and a cross-sectional view whichshow a display device of the present invention.

FIGS. 9A and 9B are a top plan view and a cross-sectional view whichshow a display device of the present invention.

FIG. 10 is a cross-sectional view showing a display device of thepresent invention.

FIG. 11 is a cross-sectional view showing a display device of thepresent invention.

FIG. 12 is a cross-sectional view showing a display device of thepresent invention.

FIG. 13 is a cross-sectional view showing a display device of thepresent invention.

FIGS. 14A and 14B are cross-sectional views each showing a displaymodule of the present invention.

FIG. 15 is a cross-sectional view showing a display module of thepresent invention.

FIGS. 16A to 16D each show a backlight applicable as a display device ofthe present invention.

FIGS. 17A to 17C are top plan views each showing a display device of thepresent invention.

FIGS. 18A and 18B are top plan views each showing a display device ofthe present invention.

FIG. 19 is a block diagram showing a main structure of an electronicappliance to which the present invention is applied.

FIGS. 20A and 20B are diagrams each showing an electronic appliance ofthe present invention.

FIGS. 21A to 21F are diagrams each showing an electronic appliance ofthe present invention.

FIGS. 22A to 22D are cross-sectional views each showing a structure of alight-emitting element applicable to the present invention.

FIGS. 23A to 23C are cross-sectional views each showing a structure of alight-emitting element applicable to the present invention.

FIGS. 24A to 24C are cross-sectional views each showing a structure of alight-emitting element applicable to the present invention.

FIG. 25 is a schematic view of the present invention.

FIGS. 26A and 26B are a top plan view and a cross-sectional view whichshow a display device of the present invention.

FIGS. 27A to 27C are cross-sectional views each showing a pyramidalprojection applicable to the present invention.

FIGS. 28A to 28C are views each showing an experimental model of acomparative example.

FIG. 29 is a graph showing an experimental data of Embodiment Mode 1.

FIG. 30 is a graph showing an experimental data of Embodiment Mode 1.

FIGS. 31A to 31C are graphs each showing an experimental data ofEmbodiment Mode 1.

FIGS. 32A to 32C are graphs each showing an experimental data ofEmbodiment Mode 1.

FIGS. 33A to 33C are graphs each showing an experimental data ofEmbodiment Mode 1.

FIGS. 34A to 34C are graphs each showing an experimental data ofEmbodiment Mode 1.

FIG. 35 is a graph showing an experimental data of Embodiment Mode 1.

FIGS. 36A to 36D are schematic views of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Although the invention will be fully described by way of embodimentmodes with reference to the accompanying drawings, it is to beunderstood by those skilled in the art that various changes andmodifications can be made without departing from the spirit and scope ofthe invention. Therefore, the present invention should not be construedas being limited to the description in the following embodiment modes.Note that common portions and portions having a similar function aredenoted by the same reference numerals in all diagrams for describingembodiment modes, and description thereof is omitted.

Embodiment Mode 1

In this embodiment mode, an example of an antireflective film having ananti-reflection function with which reflection of incident light fromexternal can be further reduced, for the purpose of providing excellentvisibility, is described.

FIGS. 1A to 1D show a top plan view and cross-sectional views of theantireflective film of the present invention. In FIGS. 1A to 1D, aplurality of pyramidal projections 451 are provided over a displayscreen surface of a display device 450. FIG. 1A is a top plan view ofthe display device of this embodiment mode. FIG. 1B is a cross-sectionalview taken along line G-H in FIG. 1A. FIG. 1C is a cross-sectional viewtaken along line I-J in FIG. 1A. FIG. 1D is a cross-sectional view takenalong line M-N in FIG. 1A. As shown in FIGS. 1A and 1B, the plurality ofpyramidal projections 451 are arranged so as to be adjacent to eachother and densely arranged over the display screen surface.

In a case where the antireflective film has a plane with respect toincident light from external (a side parallel to the display screensurface), incident light from external are reflected to the viewer side.Therefore, the antireflective film having fewer plane regions has ahigher anti-reflection function. In order that incident light fromexternal are further scattered, a plurality of sides each forming anangle with respect to a surface of the antireflective film is preferablyformed on the surface of the antireflective film.

In the present invention, since the plurality of pyramidal projectionsare geometrically arranged with no space therebetween, a refractiveindex varies from the display screen surface side to the outside (theair) due to the physical shape of a pyramidal projection. In thisembodiment mode, the tops of the plurality of pyramidal projections arearranged so as to be evenly spaced and each side of the base of apyramidal projection is in contact with one side of the base of anadjacent pyramidal projection. That is, one pyramidal projection issurrounded by other pyramidal projections, and the base of the pyramidalprojection and the base of the adjacent pyramidal projection have a sidein common.

Thus, since the pyramidal projections are arranged densely so that thetops thereof are evenly spaced, the antireflective film has a highanti-reflection function with which light from external can beefficiently scattered in many directions.

Since the plurality of pyramidal projections 451 of this embodiment modeare arranged so that the tops thereof are evenly spaced, the crosssectional surfaces of the plurality of the pyramidal projections 451have the same shape as shown in FIGS. 1B to 1D. The plurality ofpyramidal projections 451 are arranged so as to be in contact with eachother and all sides of the base of the pyramidal projection are incontact with adjacent pyramidal projections. Therefore, in thisembodiment mode, the plurality of pyramidal projections are arrangedwith no space therebetween and cover the display screen surface as shownin FIG. 1A. As shown in FIGS. 1B to 1D, a plane portion of the displayscreen surface is not exposed by the plurality of pyramidal projectionsand incident light from external is incident on sloped surfaces of theplurality of pyramidal projections, so that reflection of incident lightfrom external on the plane portion can be reduced. When the fill rate ofbases of the plurality of pyramidal projections per unit area of thedisplay screen surface is equal to or more than 80%, preferably equal toor more than 90%, the rate of light incident from external on the planeportion is reduced and thus reflection to the viewer side can beprevented.

Further, the plurality of pyramidal projections preferably have as manysides each forming an angle with respect to the bases thereof aspossible because incident light from external are scattered in many moredirections. In this embodiment mode, a pyramidal projection has sixsides which are in contact with and at an angle to a base. In addition,since the base of a pyramidal projection shares a vertex with bases ofother two pyramidal projections and the pyramidal projection has aplurality of sides which are provided at an angle, incident light ismore easily reflected in many directions. Therefore, the more verticesthe base of a pyramidal projection has, the more easily ananti-reflection function thereof can be exerted, and the pyramidalprojection of this embodiment mode has six vertices of the base. Thepyramidal projections each having a hexagonal pyramidal base of thisembodiment mode have shapes capable of being densely arranged with nospace therebetween, which are optimal shapes each having the largestnumber of sides among pyramidal projections capable of being denselyarranged with no space therebetween and a high anti-reflection functionwith which incident light can be scattered efficiently in manydirections.

Since the plurality of pyramidal projections 451 of this embodiment modeare arranged so that tops thereof are evenly spaced, cross-sectionalsurfaces of the plurality of pyramidal projections 451 of thisembodiment mode are the same shape as shown in FIGS. 1B to 1D.

FIG. 3A shows a top plan view of an example of the pyramidal projectionsof the present invention, which are densely arranged so as to beadjacent to each other, and FIG. 3B shows a cross-sectional view takenalong line K-L in FIG. 3A. A side of the base (a side of the base of apyramidal shape) of the pyramidal projection 5000 is in contact with aside of the base of each of peripheral pyramidal projections 5001 a to5001 f. Further, the pyramidal projection 5000 and the pyramidalprojections 5001 a to 5001 f arranged densely so as to surround thepyramidal projection 5000 have regular hexagonal bases and tops 5100 and5101 a to 5101 f respectively at the center of each of the regularhexagonal bases. Therefore, the top 5100 of the pyramidal projection5000 is arranged at a distance p from the tops 5101 a to 5101 f of thepyramidal projections 5001 a to 5001 f. In this case, the distance pbetween the tops of the pyramidal projections is equal to a width a ofthe pyramidal projection.

FIGS. 28A to 28C show comparative examples in a case where the presentinvention is not applied. FIG. 28A shows a structure where conicalprojections each having a circular base are densely arranged (referredto as Comparative Example 1), FIG. 28B shows a structure where pyramidalprojections each having a square base and four sides are denselyarranged (referred to as Comparative Example 2), and FIG. 28C shows astructure where pyramidal projections each having a regular trianglebase and three sides (referred to as Comparative Example 3). FIGS. 28Ato 28C are top plan views seen from above the projections. As shown inFIG. 28A, conical projections 5201 a to 5201 f are densely arrangedaround a central conical projection 5200. However, since bases of theconical projection 5200 and the conical projections 5201 a to 5201 f arecircular, spaces are left between the conical projection 5200 and theconical projections 5201 a to 5201 f and accordingly a plane displayscreen is exposed even when the conical projections are denselyarranged. Incident light from external is reflected by a plane to theviewer side; therefore, with antireflective films of the adjacentconical projections in Comparative Example 1, an anti-reflectionfunction is reduced.

In FIG. 28B, pyramidal projections 5231 a to 5231 h each having a squarebase and four sides are densely arranged in contact with a square baseof a central pyramidal projection 5230 having a square base and foursides. Similarly, in FIG. 28C, pyramidal projections 5251 a to 52511each having a regular triangle base and three sides are densely arrangedin contact with a regular triangle base of a central pyramidalprojection 5250 having a regular triangle base and three sides, Althoughthe pyramidal projections each having a regular hexagonal base and sixsides of this embodiment mode can be arranged so that the tops ofadjacent pyramidal projections are evenly spaced, pyramidal projectionsshown in Comparative Examples 2 and 3 cannot be arranged so that topsshown by dots in FIGS. 28B and 28C are evenly spaced. Since thepyramidal projections shown in Comparative Examples 2 and 3 have asmaller number of sides than the pyramidal projection of this embodimentmode, incident light cannot be easily scattered in many directions.

Optical calculations of Comparative Example 1, Comparative Example 2,and the pyramidal projection having a hexagonal base and six sides(referred to as Structure A) of this embodiment mode were performed. Anoptical calculation simulator for an optical device, Diffract MOD(manufactured by Rsoft Design Group Inc.) is used in the calculation ofthis embodiment mode. Each reflectance is calculated by 3D opticalcalculation. FIG. 29 shows a relation between the wavelength of lightand the reflectance in each of Comparative Example 1, ComparativeExample 2, and Structure A. Calculation conditions are as follows.Harmonics for both of an X direction and a Y direction, which areparameters of the above-described calculation simulator, are set to 3.In the cases of a conical projection and a hexagonal pyramidalprojection, assuming that the distance between the tops ofconical/pyramidal projections is p and the height of theconical/pyramidal projection is b, Index Res. for the X direction, the Ydirection, and a Z direction, which are parameters of theabove-described calculation simulator, are set to √3×p/128, p/128, andb/80, respectively. In the case of a square pyramidal projection,assuming that the distance between the tops of pyramidal projections isq, Index Res. for the X direction, the Y direction, and the Z direction,which are parameters of the above-described calculation simulator, areset to q/64, q/64, and b/80, respectively.

In FIG. 29, Comparative Example 1 is represented by circular dots,Comparative Example 2 is represented by quadrangular dots, and StructureA is represented by rhombic dots, and FIG. 29 shows the relation betweenthe wavelength and the reflectance in each example. Results of theoptical calculation also shows that the model in which the pyramidalprojections of Structure A, to which the present invention is applied,are densely arranged has lower reflectance than the model in whichComparative Example 1 are densely arranged and the model in whichComparative Example 2 are densely arranged in a wavelength range of 380nm to 780 nm and can reduce the reflection most largely. The refractiveindices, the heights, and the widths of Comparative Example 1,Comparative Example 2, and Structure A are 1.492, 1500 nm, and 300 nm,respectively.

When the fill rate of bases of a plurality of pyramidal projections perunit area in a surface of a display screen (that is, the substratesurface to serve as a display screen) is 80% or more, and preferably 90%or more, the percentage of incident light from external which enters aplane portion is reduced. Accordingly, incident light from external canbe prevented from being reflected to the viewer side, which ispreferable. The fill rate is a percentage of a formation region of thepyramidal projection over the substrate to serve as the display screen.When the fill rate is 80% or more, the percentage of the plane portion(which is parallel to the display screen) where the pyramidal projectionhaving a hexagonal base is not formed on the substrate surface to serveas a display screen is 20% or less.

Further, FIG. 30 shows optical calculation results of a relation betweenthe incident angle of light and the reflectance of the models in whichthe pyramidal projections each having a hexagonal base and six sides inthis embodiment mode are densely arranged. A dotted line shows therelation between the incident angle and the reflectance of a modelhaving a width of 300 nm and a height of 1500 nm, and a solid line showsthat of a model having a width of 300 nm and a height of 3000 nm. Whenthe incident angle is 60 degrees or smaller, the reflectances of themodels are suppressed to be as low as 0.003% or less. Even when theincident angle is approximately 75 degrees, the reflectances of themodels are approximately 0.01%. Thus, it can be shown that the models ofthe present invention, in which the pyramidal projections are denselyarranged, can have reduced reflectances in a wide range of incidentangle.

Similarly, the change in the reflectances of the models in which thepyramidal projections each having a hexagonal base and six sides in thisembodiment mode are densely arranged, in the case of each wavelength, iscalculated while the width a and the height b of the pyramidalprojection are changed. FIGS. 31A to 31C show the change in thereflectance R with respect to the width a when the height b is changedto 500 nm (rhombic dots), 800 nm (x dots), 1100 nm (cross dots), 1400 nm(circular dots), 1700 nm (triangular dots), and 2000 nm (quadrangulardots). FIGS. 33A to 33C show the change in the reflectance R withrespect to the height b when the width a is changed to 100 nm (rhombicdots), 160 nm (x dots), 220 nm (cross dots), 280 nm (black circulardots), 340 nm (triangular dots), 350 non (white circular dots), and 400nm (quadrangular dots). The calculations are performed in each of thecases where in a visible light range, light having a wavelength of 440nm exhibits blue color (FIGS. 31A and 33A), light having a wavelength of550 nm exhibits green color (FIGS. 31B and 33B), and light having awavelength of 620 nm exhibits red color (FIGS. 31C and 33C), and resultsof the calculations are shown.

As shown in FIGS. 31A to 31C, when the height b is 800 nm or more andthe width a is 350 nm or less (more preferably, a width a of 300 nm orless as shown in FIG. 31A), the reflectance is 0.01% or less at eachwavelength. As shown in FIGS. 33A to 33C, when the height A is 800 nm ormore, the reflectance is suppressed to be as low as 0.015% or less. Inaddition, when the height b is 1600 nm or more, the reflectance isfurther suppressed to be as low as 0.005% or less at any width a in themeasurement range.

FIGS. 32A to 32C show the change in the reflectance R with respect tothe ratio of the height b to the width a (b/a) when the height b ischanged to 500 nm (rhombic dots), 800 nm (x dots), 1100 nm (cross dots),1400 nm (circular dots), 1700 nm (triangular dots), and 2000 nm(quadrangular dots). FIGS. 34A to 34C show the change in the reflectanceR with respect to the ratio of the height b to the width a (A/a) whenthe width a is changed to 100 nm (rhombic dots), 160 nm (x dots), 220 nm(cross dots), 280 nm n (black circular dots), 340 nm (triangular dots),350 nm (white circular dots), and 400 nun (quadrangular dots). Thecalculations are performed in each of the cases where in a visible lightrange, light having a wavelengths of 440 nm exhibits blue color (FIGS.32A and 34A), light having a wavelengths of 550 nm exhibits green color(FIGS. 32B and 34B), and light having a wavelengths of 620 nm exhibitsred color (FIGS. 32C and 34C), and results of the calculations areshown.

FIG. 35 shows averaged data of the reflectance R, which includes datashown in FIGS. 34A to 34C, with respect to the ratio of the height b tothe width a (b/a) when the width a is changed from 100 nm to 400 nm.FIG. 35 shows a relation between the ratio of the height b to the widtha (b/a) and the averaged reflectance in each of the cases where thewavelength is 440 nm (rhombic dots), 550 nm (quadrangular dots), or 620mm (triangular dots). As shown in FIGS. 34A to 34C, with a height b of800 nm or more, when the ratio of the height b to the width a (b/a) isincreased, the reflectance is decreased. As shown in FIG. 35, when theratio of the height (to the width a (b/a) is equal to or more than 5,the averaged reflectance is 0.01% or less at each measurementwavelength, and thus it can be shown that the pyramidal projection inthis embodiment mode has an effect of suppressing reflection of light.

Since the distance between the tops of the plurality of pyramidalprojections is the same as the width of the plurality of pyramidalprojections, in consideration of the above, it is preferable that thedistance between the tops of the plurality of pyramidal projections be350 nm or less (more preferably, 100 nm or more and 300 nm or less) andthe height of the plurality of pyramidal projections be 800 nm or more(more preferably 1000 nm or more, and still more preferably 1600 nm ormore and 2000 nm or less). In addition, in the pyramidal projection, theratio of the height to the width of a base is preferably equal to ormore than 5.

FIGS. 2A and 2B are enlarged views of the pyramidal projection having ananti-reflection function shown in FIGS. 1A to 1D. FIG. 2A is a top planview of the pyramidal projection and FIG. 2B is a cross-sectional viewtaken along line O-P of FIG. 2A. The line O-P passes through the centerof the base of the pyramidal projection and is perpendicular to a sideof the base. As shown in FIG. 2B, a side and the base of the pyramidalprojection form an angle θ. In this specification, the length of theline which passes through the center of the base of the pyramidalprojection and is perpendicular to the side of the base is referred toas a width a of the base of the pyramidal projection. In addition, thedistance from the base of the hexagonal pyramidal projection to the topthereof is referred to as a height b of the pyramidal projection.

The shapes of a pyramidal projection may include a shape in which thetop surface of a pyramidal projection is plane and the cross sectionthereof is trapezoidal (truncated pyramid), a dome shape in which a topof a pyramidal projection is rounded, or a shape in which a prism and apyramidal projection are staked. FIGS. 27A to 27C show examples ofshapes of pyramidal projections. FIG. 27A shows the shape of a pyramidalprojection whose top is not sharp unlike the shape of the pyramidalprojection and which has a top surface (a width a₂) and a base (a widtha₁). Accordingly, a cross-sectional view showing a face which isperpendicular to the base is trapezoidal. In a pyramidal projection 491provided on a display device 490 as in FIG. 27A, the distance between alower base and an upper base is referred to as a height b in the presentinvention.

FIG. 27B shows an example in which a pyramidal projection 471 whose topis rounded is provided on a display device 470. In this manner, thepyramidal projection may have a shape with a rounded top and acurvature. In this case, a height b of the pyramidal projectioncorresponds to the distance between the base and the highest point of atop portion.

FIG. 27C shows an example in which a pyramidal projection 481 having aplurality of angles θ₁ and θ₂ is provided on a display device 480. Inthis manner, the pyramidal projection may have the shape of a stack of ahexagonal cylinder shape and a pyramidal projection shape. In this case,angles made by two sides and a base are different as shown by angles θ₁and θ₂. In the case of the projection 481 in FIG. 27C, the height bcorresponds to the height of the pyramidal shape with a sloped side ofthe pyramidal projection.

FIGS. 1A to 1D show the structure in which the plurality of pyramidalprojections are densely arranged so that bases thereof are in contactwith each other. Alternatively, a structure may be employed in which aplurality of pyramidal projections are provided on a surface which is anupper part of a film (substrate). FIGS. 36A to 36D show an example inwhich, unlike in FIGS. 1A to 1D, sides of pyramidal projections do notreach a display screen and the hexagonal pyramidal projections areprovided with the shape of a film 486 having a plurality of pyramidalprojections on the surface thereof. The antireflective film of thepresent invention is acceptable as long as it has a structure havingpyramidal projections which are densely arranged so as to be adjacent toeach other. A structure may also be employed in which pyramidalprojections are formed directly into a surface part of a film(substrate), as an integrated continuous structure. For example, asurface of a film (substrate) may be processed so that pyramidalprojections are formed thereinto, or a shape with pyramidal projectionsmay be selectively formed by a printing method such as nanoimprinting.Alternatively, pyramidal projections may be formed on a film (substrate)in another step.

The plurality of pyramidal projections may be formed as an integratedcontinuous film, or may be provided on a substrate. Alternatively,pyramidal projections may be formed into a substrate in advance. A glasssubstrate, a quartz substrate, or the like can be used as a substrate onwhich the pyramidal projections are provided. Alternatively, a flexiblesubstrate may be used. The flexible substrate refers to a substratewhich can be bent. For example, in addition to a plastic substrate madeof polycarbonate, polyarylate, polyethersulfone, or the like, elastomerwhich is a high molecular weight material, or the like, with a propertyof being plasticized at high temperature to be shaped similarly toplastic and a property of being an elastic body like a rubber at a roomtemperature can be given. Alternatively, a film (made of polypropylene,polyester, vinyl, polyvinyl fluoride, vinyl chloride, or the like), aninorganic film formed by evaporation, or the like can be used. Asubstrate may be processed so that the plurality of pyramidalprojections is formed thereinto, or the plurality of pyramidalprojections may be formed on a substrate by film formation or the like.Alternatively, the plurality of pyramidal projections may be formed inanother step and then attached to a substrate by a bonding adhesive orthe like. In the case where the antireflective film is provided on ascreen of another display device, the antireflective film can beattached by an adhesive, a bonding adhesive, or the like. As describedabove, the antireflective film of the present invention can be formed byapplication of various shapes having a plurality of pyramidalprojections.

The pyramidal projection can be formed of a material having a refractiveindex which is nonuniform and varies from the side surface toward adisplay screen. For example, in each of the plurality of pyramidalprojections, a portion closer to the side surface is formed of amaterial having a refractive index equivalent to that of the air toreduce reflection, by the side surface of the pyramidal projection, oflight incident on each pyramidal projection from external through theair. On the other hand, a portion of each of the plurality of pyramidalprojections, which is closer to the substrate on the display screenside, is formed of a material having a refractive index equivalent tothat of the substrate to further reduce reflection by an interfacebetween each pyramidal projection and the substrate, of incident lightfrom external which propagates inside each pyramidal projection and isincident on the substrate Since the refractive index of air is smallerthan that of a glass substrate, when a glass substrate is used as thesubstrate, each pyramidal projection may have such a structure in whicha portion closer to the top of the pyramidal projection is formed of amaterial having a lower refractive index and a portion closer to thebase of the pyramidal projection is formed of a material having a higherrefractive index, so that the refractive index increases from the top tothe base of the pyramidal projection.

A material used for forming the pyramidal projection may beappropriately selected in accordance with a material of the substrateforming a display screen surface, such as silicon, nitrogen, fluorine,oxide, nitride, or fluoride. As the oxide, the following can be used:silicon oxide (SiO₂), boric oxide (B₂O₃), sodium oxide (NaO₂), magnesiumoxide (MgO), aluminum oxide (alumina) (Al₂O₃), potassium oxide (K₂O),calcium oxide (CaO), diarsenic trioxide (arsenious oxide) (AS₂O₃),strontium oxide (SrO), antimony oxide (Sb₂O₃), barium oxide (BaO)₃,indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO) inwhich indium oxide is mixed with zinc oxide (ZnO), a conductive materialin which indium oxide is mixed with silicon oxide (SiO₂), organoindium,organotin, indium oxide containing tungsten oxide, indium zinc oxidecontaining tungsten oxide, indium oxide containing titanium oxide,indium tin oxide containing titanium oxide, or the like. As the nitride,aluminum nitride (AlN), silicon nitride (SiN), or the like can be used.As the fluoride, lithium fluoride (LiF), sodium fluoride (NaF),magnesium fluoride (MgF₂), calcium fluoride (CaF₂), lanthanum fluoride(LaF₃), or the like can be used. The antireflective film may include oneor more kinds of the above-described silicon, nitrogen, fluorine, oxide,nitride, and fluoride. The mixing ratio thereof may be appropriately setin accordance with the ratio of components (a composition ratio) of thesubstrate.

The pyramidal projection can be formed in such a manner that a thin filmis formed by a sputtering method, a vacuum evaporation method, a PVD(physical vapor deposition) method, or a CVD (chemical vapor deposition)method such as a low-pressure CVD (LPCVD) method or a plasma CVD method,and then etched to have a desired shape. Alternatively, a dropletdischarging method by which a pattern can be selectively formed, aprinting method by which a pattern can be transferred or drawn (a methodfor forming a pattern such as screen printing or offset printing), acoating method such as a spin coating method, a dipping method, adispensing method, a brush coating method, a spraying method, a flowcoating method, or the like may be employed. Still alternatively, animprinting technique or a nanoimprinting technique with which ananoscale three-dimensional structure can be formed by a transfertechnology may be employed. Imprinting and nanoimprinting are techniqueswith which a minute three-dimensional structure can be formed withoutusing a photolithography process.

The anti-reflection function of the antireflective film having theplurality of pyramidal projections of the present invention is explainedwith reference to FIG. 25. In FIG. 25, adjacent pyramidal projections411 a, 411 b, 411 c, and 411 d are densely provided on a display screenof a display device 410. An incident light ray 412 a from external isincident on the pyramidal projection 411 c, part of the incident lightray is transmitted through the pyramidal projection 411 c as atransmitted light ray 413 a, and the rest of the incident light ray 412a is reflected by a side surface of the pyramidal projection 411 c as areflected light ray 412 b. The reflected light ray 412 b is thenincident on the pyramidal projection 411 b which is adjacent to thepyramidal projection 411 c, part of the reflected light ray 412 b istransmitted through the pyramidal projection 411 b as a transmittedlight ray 413 b, and the rest of the reflected light ray 412 b isreflected by the side surface of the pyramidal projection 411 b as areflected light ray 412 c. The reflected light ray 412 c is thenincident on the pyramidal projection 411 c which is adjacent to thepyramidal projection 411 b, part of the incident light ray 412 c entersthe pyramidal projection 411 c as a transmitted light ray 413 c, and therest of the incident light ray 412 c is reflected by the side surface ofthe pyramidal projection 411 c as a reflected light ray 412 d. Thereflected light ray 412 d is then incident on the pyramidal projection411 b which is adjacent to the pyramidal projection 411 c, and part ofthe reflected light ray 412 d is transmitted through the pyramidalprojection 411 b as a transmitted light ray 413 d.

As described above, the antireflective film of this embodiment mode hasa plurality of pyramidal projections on the surface thereof. Reflectedincident light from external is reflected to not the viewer side butanother adjacent pyramidal projection because a side surface of eachpyramidal projection is not horizontal. Alternatively, reflectedincident light propagates between the pyramidal projections. Incidentlight from external is partly transmitted through a pyramidalprojection, and the rest of the incident light from external, which isreflected light, is then incident on an adjacent pyramidal projection.In this manner, the incident light from external which is reflected by aside surface of the pyramidal projection repeats incidence on adjacentpyramidal projections.

That is, the number of times that light from external is incident on thepyramidal projections of the antireflective film, of the incident lightfrom external which is incident on the antireflective film, isincreased; therefore, the amount of light transmitted through theantireflective film is increased. Thus, the amount of incident lightfrom external which is reflected to the viewer side is reduced, and thecause of a reduction in visibility such as reflection can be prevented.

The present invention can provide an antireflective film having ananti-reflection function with which reflection of incident light fromexternal can be further reduced by being provided with a plurality ofpyramidal projections on their surface, and a high-visibility displaydevice having such an antireflective film. Accordingly, a morehigh-quality and high-performance display device can be manufactured.

Embodiment Mode 2

In this embodiment mode, an example of a display device having ananti-reflection function with which reflection of incident light fromexternal can be further reduced, for the purpose of providing excellentvisibility, is described. More specifically, a case where the displaydevice has a passive-matrix structure is described.

The display device includes a first electrode layer 751 a, a firstelectrode layer 751 b, and a first electrode layer 751 c which extend ina first direction; an electroluminescent layer 752 which is provided tocover the first electrode layer 751 a, the first electrode layer 751 b,and the first electrode layer 751 c; and a second electrode layer 753 a,a second electrode layer 753 b, and a second electrode layer 753 c whichextend in a second direction perpendicular to the first direction (seeFIGS. 5A and 5B). The electroluminescent layer 752 is provided betweenthe first electrode layer 751 a, the first electrode layer 751 b, andthe first electrode layer 751 c and the second electrode layer 753 a,the second electrode layer 753 b, and the second electrode layer 753 c.In addition, an insulating layer 754 functioning as a protective film isprovided to cover the second electrode layer 753 a, the second electrodelayer 753 b, and the second electrode layer 753 c (see FIGS. 5A and 5B).A reference numeral 785 indicates a display element. Note that whenthere is concern about the influence of a transverse electric fieldbetween adjacent light-emitting elements, the electroluminescent layer752 provided in each light-emitting element may be separated.

FIG. 5C shows a variation on FIG. 5B, in which a first electrode layer791 a, a first electrode layer 791 b, a first electrode layer 791 c, anelectroluminescent layer 792, a second electrode layer 793 b, and aninsulating layer 794 that is a protective layer are provided on asubstrate 799. Like the first electrode layer 791 a, the first electrodelayer 791 b, and the first electrode layer 791 c in FIG. 5C, the firstelectrode layer may have a tapered shape or a shape in which a radius ofcurvature changes continuously. Shapes like the first electrode layer791 a, the first electrode layer 791 b, and the first electrode layer791 c can be formed by a droplet discharging method or the like. Whenthe first electrode layer has such a curved surface with a curvature,the coverage thereof with an insulating layer or a conductive layerwhich is stacked is favorable.

In addition, a partition (insulating layer) may be formed so as to coveran end portion of the first electrode layer. The partition (insulatinglayer) functions like a wall which separates between light-emittingelements, Each of FIGS. 6A and 6B shows a structure in which an endportion of the first electrode layer is covered with a partition(insulating layer).

In one example of a light-emitting element shown in FIG. 6A, a partition(insulating layer) 775 is formed to have a tapered shape so as to coverend portions of a first electrode layer 771 a, a first electrode layer771 b, and a first electrode layer 771 c. The partition (insulatinglayer) 775 is formed over the first electrode layer 771 a, the firstelectrode layer 771 b, and the first electrode layer 771 c which areprovided in contact with a substrate 779, and an electroluminescentlayer 772, a second electrode layer 773 b, an insulating layer 774, aninsulating layer 776, and a substrate 778 are provided.

In one example of a light-emitting element shown in FIG. 613, apartition (insulating layer) 765 has a shape having a curvature, inwhich a radius of curvature changes continuously. The partition 765 isprovided in contact with a first electrode layer 761 a, a firstelectrode layer 761 b, a first electrode layer 761 c, anelectroluminescent layer 762, a second electrode layer 763 b, aninsulating layer 764, and a protective layer 768.

FIG. 4 shows a passive-matrix liquid crystal display device to which thepresent invention is applied. In FIG. 4, a substrate 1700 provided withfirst pixel electrode layers 1701 a, 1701 b, and 1701 c, and aninsulating layer 1712 functioning as an orientation film faces asubstrate 1710 provided with an insulating layer 1704 functioning as anorientation film, a counter electrode layer 1705, a colored layer 1706functioning as a color filter, and a polarizing plate 1714, with aliquid crystal layer 1703 interposed therebetween.

In the present invention, in order that the display screen surface ofthe display device may be provided with an anti-reflection function withwhich reflection of incident light from external is prevented, aplurality of pyramidal projections are densely arranged on the displayscreen surface. In this embodiment mode, pyramidal projections 757, 797,777, 767, and 1707 are provided on surfaces of substrates 758, 798, 778,769, and 1710, respectively.

The display device of this embodiment mode is acceptable as long as ithas a structure having pyramidal projections which are densely arrangedso as to be adjacent to each other. A structure may be employed in whichpyramidal projections are formed directly into a surface part of asubstrate (film) forming the display screen, as an integrated continuousstructure. For example, a surface of a substrate (film) may be processedso that pyramidal projections are formed thereinto, or a shape withpyramidal projections may be selectively formed by a printing methodsuch as nanoimprinting. Alternatively, pyramidal projections may beformed on a substrate (film) in another step.

The plurality of pyramidal projections may be formed as an integratedcontinuous film, or may be densely arranged on a substrate.Alternatively, pyramidal projections may be formed into a substrate inadvance. FIG. 6A is an example in which a plurality of pyramidalprojections 777 are provided on a surface of a substrate 778 as anintegrated continuous structure.

In a case where the display screen has a plane with respect to incidentlight from external (a side parallel to the display screen), incidentlight from external are reflected to the viewer side. Therefore, thedisplay screen having fewer plane regions has a higher anti-reflectionfunction. In order that incident light from external are furtherscattered, a plurality of sides each forming an angle with respect to asurface of the display screen are preferably formed on the surface ofthe display screen.

In the present invention, since the plurality of pyramidal projectionsare densely arranged with no space therebetween, a refractive indexvaries from the display screen surface side to the outside (the air) dueto the physical shape of a pyramidal projection. In this embodimentmode, the tops of the plurality of pyramidal projections are arranged soas to be evenly spaced and each side of the base of a pyramidalprojection is in contact with one side of the base of an adjacentpyramidal projection. That is, one pyramidal projection is surrounded byother pyramidal projections, and the base of the pyramidal projectionand the base of the adjacent pyramidal projection have a side in common.

Thus, since the pyramidal projections are arranged densely so that thetops thereof are evenly spaced, the display screen has a highanti-reflection function with which incident light from external can beefficiently scattered in many directions.

Since a plurality of the pyramidal projections 451 of this embodimentmode are arranged so that the tops thereof are evenly spaced, the crosssectional surfaces of the plurality of the pyramidal projections 451have the same shape as shown in FIGS. 4, 5A to 5C, 6A, and 6B. Theplurality of the pyramidal projections 451 are arranged so as to be incontact with each other and each side of the base of the pyramidalprojection is in contact with one side of the base of the adjacentpyramidal projection. Therefore, in this embodiment mode, the pluralityof pyramidal projections are arranged with no space therebetween andcover the display screen surface as shown in FIGS. 4, 5A to 5C, 6A, and6B. A plane portion of the display screen surface is not exposed by theplurality of pyramidal projections and incident light from external isincident on sloped surfaces of the plurality of pyramidal projections,so that reflection of incident light from external on the plane portioncan be reduced.

In this embodiment mode, the distance between the tops of the pluralityof pyramidal projections and the width of the base of the pyramidalprojection are preferably equal to or shorter than 350 nm, and theheight of each of the plurality of pyramidal projections is preferablyequal to or longer than 800 nm. The fill rate of bases of the pluralityof pyramidal projections per unit area of a display screen (the rate ofthe display screen which is filled (occupied)) is equal to or more than80%, preferably equal to or more than 90%. A fill rate is a rate of aformation region of pyramidal projections on a display screen. When thefill rate is equal to or more than 80%, the rate of plane portions whereno pyramidal projection is formed (which is parallel to the displayscreen) is equal to or less than 20%. The ratio of the height of apyramidal projection to the width of a base thereof is preferably equalto or more than 5. Under the above-described condition, the rate oflight incident from external on the plane portion is reduced and thusreflection with respect to the viewer side can be prevented.

Further, the plurality of pyramidal projections preferably have as manysides each forming an angle with respect to the bases thereof aspossible because incident light from external are scattered in many moredirections. In this embodiment mode, a pyramidal projection has sixsides which are in contact with and at an angle to a base. In addition,since the base of a pyramidal projection shares a vertex with bases ofother two pyramidal projections and the pyramidal projection has aplurality of sides which are provided at an angle, incident light ismore easily reflected in many directions. Therefore, the more verticesthe base of a pyramidal projection has, the more easily ananti-reflection function thereof can be exerted, and the pyramidalprojection of this embodiment mode has six vertices of the base. Thepyramidal projections each having a hexagonal pyramidal base of thisembodiment mode have shapes capable of being densely arranged with nospace therebetween, which are optimal shapes each having the largestnumber of sides among pyramidal projections capable of being denselyarranged with no space therebetween and a high anti-reflection functionwith which incident light can be scattered efficiently in manydirections.

Since the plurality of pyramidal projections 757, 797, 777, 767, and1707 are provided so that the tops thereof are evenly spaced, thecross-sectional views thereof are isosceles triangles. Each of thecross-sectional views is taken along line O-P in the top plan view ofFIG. 2A of Embodiment Mode 1. In this specification, when thecross-sectional view of the pyramidal projection is shown, it is a crosssection taken along line including a perpendicular line dropped from acenter of the base (an intersection of diagonal lines) of the pyramidalprojection to a side of the base as the pyramidal projection 451 is cutalong line O-P in FIG. 2A.

The pyramidal projection can be formed of a material having a refractiveindex which is nonuniform and varies from the side surface toward adisplay screen. For example, in each of the plurality of pyramidalprojections, a portion closer to the side surface is formed of amaterial having a refractive index equivalent to that of the air toreduce reflection, by the side surface of the pyramidal projection, oflight incident on each pyramidal projection from external through theair. On the other hand, a portion of each of the plurality of pyramidalprojections, which is closer to the substrate on the display screenside, is formed of a material having a refractive index equivalent tothat of the substrate to further reduce reflection by an interfacebetween each pyramidal projection and the substrate, of incident lightfrom external which propagates inside each pyramidal projection and isincident on the substrate Since the refractive index of air is smallerthan that of a glass substrate, when a glass substrate is used as thesubstrate, each pyramidal projection may have such a structure in whicha portion closer to the top of the pyramidal projection is formed of amaterial having a lower refractive index and a portion closer to thebase of the pyramidal projection is formed of a material having a higherrefractive index, so that the refractive index increases from the top tothe base of the pyramidal projection.

A material used for forming the pyramidal projection may beappropriately selected in accordance with a material of the substrateforming a display screen surface, such as silicon, nitrogen, fluorine,oxide, nitride, or fluoride. As the oxide, the following can be used:silicon oxide (SiO₂), boric oxide (B₂O₃), sodium oxide (NaO₂), magnesiumoxide (MgO), aluminum oxide (alumina) (Al₂O₃), potassium oxide (K₂O),calcium oxide (CaO), diarsenic trioxide (arsenious oxide) (As₂O₃),strontium oxide (SrO), antimony oxide (Sb₂O₃), barium oxide (BaO),indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO) inwhich indium oxide is mixed with zinc oxide (ZnO), a conductive materialin which indium oxide is mixed with silicon oxide (SiO₂), organoindium,organotin, indium oxide containing tungsten oxide, indium zinc oxidecontaining tungsten oxide, indium oxide containing titanium oxide,indium tin oxide containing titanium oxide, or the like. As the nitride,aluminum nitride (AlN), silicon nitride (SiN), or the like can be used.As the fluoride, lithium fluoride (LiF), sodium fluoride (NaF),magnesium fluoride (MgF₂), calcium fluoride (CaF₂), lanthanum fluoride(LaF₃), or the like can be used. The antireflective film may include oneor more kinds of the above-described silicon, nitrogen, fluorine, oxide,nitride, and fluoride. The mixing ratio thereof may be appropriately setin accordance with the ratio of components (a composition ratio) of thesubstrate. Alternatively, a material, which is described above as amaterial of the substrate, may be used.

The pyramidal projection can be formed in such a manner that a thin filmis formed by a sputtering method, a vacuum evaporation method, a PVD(physical vapor deposition) method, or a CVD (chemical vapor deposition)method such as a low-pressure CVD (LPCVD) method or a plasma CVD method,and then etched to have a desired shape. Alternatively, a dropletdischarging method by which a pattern can be selectively formed, aprinting method by which a pattern can be transferred or drawn (a methodfor forming a pattern such as screen printing or offset printing), acoating method such as a spin coating method, a dipping method, adispensing method, a brush coating method, a spraying method, a flowcoating method, or the like may be employed. Still alternatively, animprinting technique or a nanoimprinting technique with which ananoscale three-dimensional structure can be formed by a transfertechnology may be employed. Imprinting and nanoimprinting are techniqueswith which a minute three-dimensional structure can be formed withoutusing a photolithography process.

The display device of this embodiment mode has a plurality of pyramidalprojections on the surface thereof. Reflected incident light fromexternal is reflected to not the viewer side but another adjacentpyramidal projection because a side surface of each pyramidal projectionis not horizontal. Alternatively, reflected incident light propagatesbetween adjacent pyramidal projections. Incident light from external ispartly transmitted through a pyramidal projection, and the rest of theincident light from external, which is reflected light, is then incidenton an adjacent pyramidal projection. In this manner, the incident lightfrom external which is reflected by a side surface of the pyramidalprojection repeats incidence on adjacent pyramidal projections.

That is, the number of times that incident light from external isincident on the pyramidal projections, of the incident light fromexternal which is incident on the display device, is increased;therefore, the amount of light transmitted through the pyramidalprojections is increased. Thus, the amount of incident light fromexternal which is reflected to the viewer side is reduced, and the causeof a reduction in visibility such as reflection can be prevented.

A glass substrate, a quartz substrate, or the like can be used as eachof the substrates 758, 759, 769, 778, 779, 798, 799, 1700, and 1710.Alternatively, a flexible substrate may be used. The flexible substraterefers to a substrate which can be bent. For example, in addition to aplastic substrate made of polycarbonate, polyarylate, polyethersulfone,or the like, elastomer which is a high molecular weight material, or thelike, with a property of being plasticized at high temperature to beshaped similarly to plastic and a property of being an elastic body likea rubber at a room temperature can be given. Alternatively, a film (madeof polypropylene, polyester, vinyl, polyvinyl fluoride, vinyl chloride,or the like), an inorganic film formed by evaporation, or the like canbe used.

The partition (insulating layer) 765 and the partition (insulatinglayer) 775 may be formed using an inorganic insulating material such assilicon oxide, silicon nitride, silicon oxynitride, aluminum oxide,aluminum nitride, or aluminum oxynitride; an acrylic acid, a methacrylicacid, or a derivative thereof; a heat-resistant high molecule such aspolyimide, aromatic polyamide, or polybenzimidazole; or a siloxane resinmay be used. Other resin materials such as a vinyl resin, for example,polyvinyl alcohol or polyvinyl butyral, an epoxy resin, a phenol resin,a novolac resin, an acrylic resin, a melamine resin, and a urethaneresin may be used. Alternatively, an organic material such asbenzocyclobutene, parylene, fluorinated arylene ether, or polyimide, ora composition material containing water-soluble homopolymers andwater-soluble copolymers may be used. As a manufacturing method, a vapordeposition method such as a plasma CVD method or a thermal CVD method,or a sputtering method can be used. Alternatively, a droplet dischargingmethod or a printing method (a method for forming a pattern, such asscreen printing or offset printing) may be used. A film obtained by acoating method, an SOG film, or the like may be used.

After a conductive layer, an insulating layer, or the like is formed bydischarging a composition by a droplet-discharging method, a surfacethereof may be planarized by being pressed with pressure to enhance alevel of planarity, As a pressing method, scanning of the surface by aroller-shaped object to reduce concavity and convexity of the surface;using a flat plate-shaped object to press the surface; or the like canbe given. When pressing the surface, a heating step may be performed.Alternatively, concavity and convexity of the surface may be removedwith an air knife after the surface is softened or melted with a solventor the like. Alternatively, a CMP method may be used for polishing thesurface. This step can be employed to planarize the surface when thesurface becomes uneven due to a droplet-discharging method.

This embodiment mode can provide a high-visibility display device havingan anti-reflection function with which reflection of incident light fromexternal can be further reduced by being provided with a plurality ofpyramidal projections on their surface. Accordingly, a more high-qualityand high-performance display device can be manufactured.

This embodiment mode can be freely combined with Embodiment Mode 1.

Embodiment Mode 3

In this embodiment mode, an example of a display device having ananti-reflection function with which reflection of incident light fromexternal can be further reduced, for the purpose of providing excellentvisibility, is described. In this embodiment mode, a display devicehaving a different structure from that of Embodiment Mode 2 isdescribed. Specifically, a case where the display device has anactive-matrix structure is described.

FIG. 26A shows a top plan view of the display device, and FIG. 26B showsa cross-sectional view taken along line E-F in FIG. 26A. Although anelectroluminescent layer 532, a second electrode layer 533, and aninsulating layer 534 are omitted and not shown in FIG. 26A, each of themis provided as shown in FIG. 26B.

First wirings that extend in a first direction and second wirings thatextend in a second direction perpendicular to the first direction areprovided over a substrate 520 provided with an insulating layer 523 as abase film. One of the first wirings is connected to a source electrodeor a drain electrode of a transistor 521, and one of the second wiringsis connected to a gate electrode of the transistor 521. A firstelectrode layer 531 is connected to a wiring layer 525 b that is thesource electrode or the drain electrode of the transistor 521, which isnot connected to the first wiring, and a light-emitting element 530 isformed using a stacked-layer structure of the first electrode layer 531,the electroluminescent layer 532, and the second electrode layer 533. Apartition (insulating layer) 528 is provided between adjacentlight-emitting elements, and the electroluminescent layer 532 and thesecond electrode layer 533 are stacked over the first electrode layerand the partition (insulating layer) 528. An insulating layer 534functioning as a protective layer and a substrate 538 functioning as asealing substrate are provided over the second electrode layer 533. Asthe transistor 521, an inversed staggered thin film transistor is used(see FIGS. 26A and 26B). Light emitted from the light-emitting element530 is extracted from the substrate 538 side. Thus, a surface of thesubstrate 538 on the viewer side is provided with a plurality ofpyramidal projections 529 of the present invention.

FIGS. 26A and 26B in this embodiment mode show an example in which thetransistor 521 is a channel-etch inversed-staggered transistor. In FIGS.26A and 26B, the transistor 521 includes a gate electrode layer 502, agate insulating layer 526, a semiconductor layer 504, semiconductorlayers 503 a and 503 b having one conductivity type, and wiring layers525 a and 525 b serving as source and drain electrode layers.

A material for forming the semiconductor layer can be an amorphoussemiconductor (hereinafter also referred to as “AS”) formed by a vapordeposition method using a semiconductor material gas typified by silaneor germane or a sputtering method, a polycrystalline semiconductorformed by crystallization of the amorphous semiconductor with the use oflight energy or thermal energy, a semi-amorphous semiconductor (alsoreferred to as microcrystal and hereinafter also referred to as “SAS”),or the like.

An SAS is a semiconductor having an intermediate structure between anamorphous structure and a crystalline structure (including singlecrystal and polycrystal) and a third state which is stable in freeenergy. Moreover, an SAS includes a crystalline region with ashort-distance order and lattice distortion. An SAS is formed by glowdischarge decomposition (plasma CVD) of a gas containing silicon. As thegas containing silicon, SiH₄, Si₂H₆, SiH₂Cl₂, SiHCl₃, SiCl₄, SiF₄, orthe like can be used. Further, F₂ or GeF₄ may be mixed. The gascontaining silicon may be diluted with H₂, or H₂ and one or a pluralityof kinds of rare gas elements selected from He, Ar, Kr, and Ne. Further,when a rare gas element such as helium, argon, krypton, or neon iscontained to further promote the lattice distortion, stability can beenhanced, and a favorable SAS can be obtained. Further, as thesemiconductor layer, an SAS layer formed using a hydrogen-based gas maybe stacked over an SAS layer formed using a fluorine-based gas.

As a typical example of an amorphous semiconductor, hydrogenatedamorphous silicon can be given, and polysilicon or the like can be givenas a typical example of a crystalline semiconductor. Polysilicon(polycrystalline silicon) may be so-called high-temperature polysiliconformed using polysilicon which is formed at processing temperatures of800° C. or higher as a main material, so-called low-temperaturepolysilicon formed using polysilicon which is formed at processingtemperatures of 600° C. or lower as a main material, polysiliconcrystallized by the addition of an element which promotescrystallization, or the like. It is needless to say that asemi-amorphous semiconductor or a semiconductor which includes acrystalline phase in a portion thereof may be used as described above.

When a crystalline semiconductor layer is used for the semiconductorlayer, the crystalline semiconductor layer may be formed by knownmethods (a laser crystallization method, a thermal crystallizationmethod, a thermal crystallization method using an element such as nickelwhich promotes crystallization, and the like). Further, amicrocrystalline semiconductor that is an SAS may be crystallized bylaser irradiation to enhance crystallinity. In the case where an elementwhich promotes crystallization is not introduced, before the amorphoussilicon layer is irradiated with laser light, the amorphoussemiconductor layer is heated at 500° C. for one hour in a nitrogenatmosphere to discharge hydrogen so that a hydrogen concentration in theamorphous semiconductor layer is 1×10²⁰ atoms/cm³ or lower. This isbecause, if the amorphous semiconductor layer contains a lot ofhydrogen, the amorphous semiconductor layer may be damaged by laser beamirradiation. The heat treatment for crystallization can be performedusing a heating furnace, laser irradiation, irradiation with lightemitted from a lamp (also referred to as lamp annealing), or the like.An example of a heating method is an RTA method such as a GRTA (gasrapid thermal annealing) method or an LRTA (lamp rapid thermalannealing) method. GRTA is a method for performing a heat treatmentusing a high-temperature gas, and LRTA is a method for performing a heattreatment by lamp light.

In a crystallization step in which an amorphous semiconductor layer iscrystallized to form a crystalline semiconductor layer, an element whichpromotes crystallization (also referred to as a catalytic element or ametal element) is added to the amorphous semiconductor layer, andcrystallization may be performed by heat treatment (at 550 to 750° C.for 3 minutes to 24 hours). As an element which promotes crystallizationof silicon, one or a plurality of kinds of metals selected from iron(Fe), nickel (Ni), cobalt (Co), ruthenium (Ru), rhodium (Rh), palladium(Pd), osmium (Os), iridium (Ir), platinum (Pt), copper (Cu), and gold(Au) can be used.

There is no particular limitation on a method for introducing a metalelement into the amorphous semiconductor layer as long as it is a methodfor introducing the metal element to a surface or inside of theamorphous semiconductor layer. For example, a sputtering method, a CVDmethod, a plasma treatment method (including a plasma CVD method), anadsorption method, or a method for applying a solution of metal salt canbe used. Among these methods, a method using a solution is simple andadvantageous in that the concentration of the metal element can beeasily controlled. At this time, it is desirable to form an oxide filmby UV light irradiation in an oxygen atmosphere, a thermal oxidationmethod, treatment with ozone water containing hydroxyl radical orhydrogen peroxide, or the like to improve wettability of the surface ofthe amorphous semiconductor layer so that an aqueous solution isdiffused on the entire surface of the amorphous semiconductor layer.

In order to remove the element which promotes crystallization from thecrystalline semiconductor layer or reduce the amount of the elementwhich promotes crystallization in the crystalline semiconductor layer, asemiconductor layer containing an impurity element is formed to be incontact with the crystalline semiconductor layer and is made to functionas a gettering sink. As the impurity element, an impurity elementimparting n-type conductivity, an impurity element imparting p-typeconductivity, a rare gas element, or the like can be used. For example,one or a plurality of kinds of elements selected from phosphorus (P),nitrogen N), arsenic (As), antimony (Sb), bismuth (Bi), boron (B),helium (He), neon (Se), argon (Ar), krypton (Kr), and xenon (Xe) can beused. A semiconductor layer containing a rare gas element is formed tobe in contact with the crystalline semiconductor layer containing theelement which promotes crystallization, and heat treatment (at 550 to750° C. for 3 minutes to 24 hours) is performed. The element whichpromotes crystallization contained in the crystalline semiconductorlayer moves into the semiconductor Layer containing a rare gas element,and the element which promotes crystallization contained in thecrystalline semiconductor layer is removed or reduced. After that, thesemiconductor layer containing a rare gas element, which is made tofunction as a gettering sink, is removed.

Laser irradiation can be performed by relatively moving a laser beam andthe semiconductor layer. In laser irradiation, a marker can also beformed in order to overlap a beam with high accuracy or control a startposition or an end position of laser irradiation. The marker may beformed over the substrate at the same time as the formation of theamorphous semiconductor layer.

In the case of using laser irradiation, a continuous wave laser beam (aCW laser beam) or a pulsed wave laser beam (a pulsed laser beam) can beused. As a laser beam which can be used here, a laser beam emitted fromone or more of the following can be used: a gas laser such as an Arlaser, a Kr laser, or an excimer laser; a laser of which medium issingle crystalline YAG, YVO₄, forsterite (Mg₂SiO₄), YAlO₃, or GdVO₄, orpolycrystalline (ceramic) YAG, Y₂O₃, YVO₄, YAlO₃, or GdVO₄, added withone or more of Nd, Yb, Cr, Ti, Ho, Er, Tm, and Ta as a dopant; a glasslaser; a ruby laser; an alexandrite laser; a Ti:sapphire laser; a coppervapor laser; or a gold vapor laser. It is possible to obtain crystalswith a large grain size when fundamental waves of such laser beams orsecond to fourth harmonics of the fundamental waves are used. Forexample, the second harmonic (532 nm) or the third harmonic (355 nm) ofan Nd:YVO₄ laser (fundamental wave of 1064 nm) can be used. The laserbeam may be either a CW laser beam or a pulsed laser beam. In the caseof a CW laser beam, a power density of approximately 0.01 to 100 MW/cm²(preferably, 0.1 to 10 MW/cm²) is necessary. Irradiation is conducted ata scanning rate of approximately 10 to 2000 cm/sec.

It is to be noted that, a laser using, as a medium, single crystallineYAG, YVO₄, forsterite (Mg₂SiO₄), YAlO₃, or GdVO₄, or polycrystalline(ceramic) YAG, Y₂O₃, YVO₄, YAlO₃, or GdVO₄ added with one or more of Nd,Yb, Cr, Ti, Ho, Er, Tm, and Ta as a dopant; an Ar ion laser; or aTi:sapphire laser can be continuously oscillated. Furthermore, pulseoscillation thereof can be performed at a repetition rate of 10 MHz ormore by carrying out Q switch operation, mode locking, or the like. In acase where a laser beam is oscillated at a repetition rate of 10 MHz ormore, after a semiconductor layer is melted by a laser and before it issolidified, the semiconductor layer is irradiated with a next pulse.Therefore, unlike a case of using a pulsed laser with a low repetitionrate, a solid-liquid interface can be continuously moved in thesemiconductor layer, so that crystal grains which continuously grow in ascanning direction can be obtained.

When ceramic (polycrystal) is used as a medium, the medium can be formedinto a desired shape in a short time at low cost. In the case of using asingle crystal, a columnar medium having a diameter of severalmillimeters and a length of several tens of millimeters is generallyused. However, in the case of using ceramic, a larger medium can beformed.

A concentration of a dopant such as Nd or Yb in a medium, which directlycontributes to light emission, cannot be changed largely either in asingle crystal or a polycrystal. Therefore, there is limitation to someextent on improvement in laser output by increasing the concentration.However, in the case of using ceramic, the size of the medium can besignificantly increased compared with the case of using a singlecrystal, and thus, significant improvement in output can be achieved.

Furthermore, in the case of using ceramic, a medium having aparallelepiped shape or a rectangular solid shape can be easily formed.When a medium having such a shape is used and emitted light propagatesinside the medium in zigzags, an emitted light path can be extended.Therefore, the light is amplified largely and can be emitted with highoutput. In addition, since a laser beam emitted from a medium havingsuch a shape has a quadrangular shape in cross section at the time ofemission, it has an advantage over a circular beam in being shaped intoa linear beam. By shaping the laser beam emitted as described aboveusing an optical system, a linear beam having a length of 1 mm or lesson a shorter side and a length of several millimeters to several meterson a longer side can be easily obtained. Further, by uniformlyirradiating the medium with excited light, the linear beam has a uniformenergy distribution in a long-side direction. Moreover, thesemiconductor layer is preferably irradiated with the laser beam at anincident angle θ (0°<θ<90°) because laser interference can be prevented.

By irradiating the semiconductor layer with this linear beam, the entiresurface of the semiconductor layer can be annealed more uniformly. Whenuniform annealing is needed to both ends of the linear beam, a devisalsuch as utilization of slits for shielding a portion where energy isdecayed against light is necessary.

When the linear beam with uniform intensity, which is obtained asdescribed above, is used for annealing the semiconductor layer and adisplay device is manufactured using this semiconductor layer, thedisplay device have favorable and uniform characteristics.

Alternatively, laser light irradiation may be performed in an inactivegas atmosphere of a rare gas, nitrogen, or the like. By the laser lightirradiation, unevenness of a surface of the semiconductor layer can besuppressed, and variation in the threshold voltage of a transistor,which is caused due to variation in interface state density, can besuppressed.

The amorphous semiconductor layer may be crystallized by a combinationof heat treatment and laser light irradiation, or several times of heattreatment or laser light irradiation.

The gate electrode layer can be formed by a sputtering method, anevaporation method, a CVD method, or the like. The gate electrode layermay be formed using an element selected from tantalum (Ta), tungsten(W), titanium (Ti), molybdenum (Mo), aluminum (Al), copper (Cu),chromium (Cr), and neodymium (Nd), or an alloy material or a compoundmaterial containing these elements as its main component. Alternatively,as the gate electrode layer, a semiconductor film typified by apolycrystalline silicon film doped with an impurity element such asphosphorus, or AgPdCu alloy may be used. The gate electrode layer mayhave a single-layer structure or a stacked-layer structure.

In this embodiment mode, the gate electrode layer is formed into atapered shape; however, the present invention is not limited thereto.The gate electrode layer may have a stacked layer structure, where onlyone layer has a tapered shape while the other is given a perpendicularside surface by anisotropic etching. The taper angles may differ betweenthe stacked gate electrode layers or may be the same. Due to the taperedshape, coverage by a film that is stacked thereover is improved anddefects are reduced; therefore, reliability is enhanced.

In order to form a source electrode layer or drain electrode layer, aconductive film is formed by a PVD method, a CVD method, an evaporationmethod, or the like, and the conductive film is etched to have a desiredshape. Then, a conductive layer can be selectively formed in apredetermined position by a droplet discharging method, a printingmethod, a dispenser method, an electrolytic plating method, or the like.Alternatively, a reflow method or a damascene method may be used. Thesource electrode layer or drain electrode layer is formed using aconductive material such as a metal, specifically, Ag, Au, Cu, Ni, Pt,Pd, Ir, Rh, W, Al, Ta, Mo, Cd, Zn, Fe, Ti, Zr, Ba, Si, or Ge or an alloyor nitride thereof. Alternatively, a stacked-layer structure of thesematerials may be used.

The insulating layers 523, 526, 527, and 534 may be formed using aninorganic insulating material such as silicon oxide, silicon nitride,silicon oxynitride, aluminum oxide, aluminum nitride, or aluminumoxynitride; an acrylic acid, a methacrylic acid, or a derivativethereof; a heat-resistant high molecule such as polyimide, aromaticpolyamide, or polybenzimidazole; or a siloxane resin may be used. Otherresin materials such as a vinyl resin, for example, polyvinyl alcohol orpolyvinyl butyral, an epoxy resin, a phenol resin, a novolac resin, anacrylic resin, a melamine resin, and a urethane resin may be used.Alternatively, an organic material such as benzocyclobutene, parylene,fluorinated arylene ether, or polyimide, or a composition materialcontaining water-soluble homopolymers and water-soluble copolymers maybe used. As a manufacturing method, a vapor deposition method such as aplasma CVD method or a thermal CVD method, or a sputtering method can beused. Alternatively, a droplet discharging method, a dispenser method,or a printing method (a method for forming a pattern, such as screenprinting or offset printing) may be used. A film obtained by a coatingmethod, an SOG film, or the like may be used.

The structure of the thin film transistor is not limited to that of thisembodiment mode. A single-gate structure in which one channel formationregion is formed, a double-gate structure in which two channel formationregions are formed, or a triple-gate structure in which three channelformation regions are formed may be employed. Further, the thin filmtransistor in the peripheral driver circuit region may also employ asingle gate structure, a double gate structure, or a triple gatestructure.

It is to be noted the present invention is not limited to the thin filmtransistor described in this embodiment mode, and may be applied to atop gate structure (such as a staggered type or a coplanar type), abottom gate structure (such as an inverse coplanar type), a dual gatestructure in which two gate electrode layers are arranged above or belowa channel formation region, each with a gate insulating film interposedtherebetween, or another structure.

Each of FIGS. 7A and 7B shows an active-matrix liquid crystal displaydevice to which the present invention is applied. In each of FIGS. 7Aand 7B, a substrate 550 provided with a transistor 551 having amulti-gate structure, a pixel electrode layer 560, and an insulatinglayer 561 functioning as an orientation film faces a substrate 568provided with an insulating layer 563 functioning as an orientationfilm, a conductive layer 564 functioning as a counter electrode layer, acolored layer 565 functioning as a color filter, and a substrate 568provided with a polarizer (also referred to as a polarizing plate) 556,with a liquid crystal layer 562 interposed therebetween. A surface ofthe substrate 568 on the viewer side is provided with a plurality ofpyramidal projections 567 of the present invention.

An example where the transistor 551 is a multigate channel-etchinversed-staggered transistor is described. In FIGS. 7A and 7B, thetransistor 551 includes gate electrode layers 552 a and 552 b, a gateinsulating layer 558, a semiconductor layer 554, semiconductor layers553 a, 553 b, and 553 c having one conductivity type, and wiring layers555 a, 555 h, and 555 c each serving as a source electrode layer or adrain electrode layer. An insulating layer 557 is provided over atransistor 551.

The display device of FIG. 7A is an example in which the plurality ofpyramidal projections 567 are provided on an outer side of the substrate568, and the polarizer 556, the colored layer 565, and the conductivelayer 564 are sequentially provided on an inner side. However, thepolarizer 569 may be provided on the outer side of the substrate 568 (onthe viewer side) as shown in FIG. 7B, and in that case, the plurality ofpyramidal projections 567 may be provided on a surface of the polarizer569. The stacked-layer structure of the polarizer and the colored layeris also not limited to that of FIG. 7A and may be appropriatelydetermined depending on materials of the polarizer and the colored layeror conditions of a manufacturing process.

FIG. 13 shows an active matrix type electronic paper to which thepresent invention is applied. Although FIG. 13 shows an active matrixtype, the present invention can also be applied to a passive matrixtype.

Although FIGS. 7A and 7B show examples using a liquid crystal displayelement as a display element, a display device using a twist balldisplay mode may be used. A twist ball display mode means a method inwhich spherical particles each colored in black and white are arrangedbetween a first electrode layer and a second electrode layer, and apotential difference is generated between the first electrode layer andthe second electrode layer to control directions of the sphericalparticles, so that display is performed.

A transistor 581 is an inverse coplanar thin film transistor, andincludes a gate electrode layer 582, a gate insulating layer 584, wiringlayers 585 a and 585 b, and a semiconductor layer 586. In addition, thewiring layer 585 b is in contact with and electrically connected tofirst electrode layers 587 a through an opening formed in an insulatinglayer 598. Between the first electrode layers 587 a, and a secondelectrode layer 588, spherical particles 589 each including a blackregion 590 a and a white region 590 b, and a cavity 594 filled withliquid around the black region 590 a and the white region 590 b areprovided. The circumference of the spherical particle 589 is filled witha filler 595 such as a resin or the like (see FIG. 13). The plurality ofpyramidal projections 597 of the present invention are provided on asurface of a substrate 596 on the viewer side.

Instead of the twist ball, an electrophoretic element may be used. Amicrocapsule having a diameter of approximately 10 to 20 μm in whichtransparent liquid, positively charged white microparticles, andnegatively charged black microparticles are encapsulated is used. In themicrocapsule provided between the first electrode layer and the secondelectrode layer, when an electric field is applied by the firstelectrode layer and the second electrode layer, the white microparticlesand black microparticles move to opposite sides from each other, so thatwhite or black can be displayed. A display element using this principleis an electrophoretic display element and is called an electronic paperin general. The electrophoretic display element has higher reflectivitythan a liquid crystal display element, and thus an assistant light isunnecessary, power consumption is low, and a display portion can berecognized even in a dim place. Further, even when electric power is notsupplied to the display portion, an image which has been displayed oncecan be stored. Thus, a displayed image can be stored even if asemiconductor device having a display function is distanced from asource of an electronic wave.

The transistor may have any structure as long as the transistor canfunction as a switching element. As a semiconductor layer, varioussemiconductors such as an amorphous semiconductor, a crystallinesemiconductor, a polycrystalline semiconductor, and a microcrystalsemiconductor may be used, or an organic transistor may be formed usingan organic compound.

The display device of this embodiment mode is acceptable as long as ithas a structure having pyramidal projections which are densely arrangedso as to be adjacent to each other. A structure may be employed in whichpyramidal projections are formed directly into a surface part of asubstrate (film) forming the display screen, as an integrated continuousstructure. For example, a surface of a substrate (film) may be processedso that pyramidal projections are formed thereinto, or a shape withpyramidal projections may be selectively formed by a printing methodsuch as nanoimprinting. Alternatively, pyramidal projections may beformed on a substrate (film) in another step.

The plurality of pyramidal projections may be formed as an integratedcontinuous film, or may be densely arranged on a substrate.

In this embodiment mode, the display device has the plurality ofpyramidal projections on the display screen surface provided with ananti-reflection function with which reflection of incident light fromexternal is prevented. In a case where the display screen has a planewith respect to incident light from external (a side parallel to thedisplay screen surface), incident light from external are reflected tothe viewer side. Therefore, the display screen having fewer planeregions has a higher anti-reflection function. In order that incidentlight from external are further scattered, a plurality of sides eachforming an angle with respect to a surface of the display screen ispreferably formed on the surface of the display screen.

In the present invention, since the plurality of pyramidal projectionsare geometrically densely arranged with no space therebetween, arefractive index varies from the display screen surface side to theoutside (the air) due to the physical shape of a pyramidal projection.In this embodiment mode, the tops of the plurality of pyramidalprojections are arranged so as to be evenly spaced and each side of thebase of a pyramidal projection is in contact with one side of the baseof an adjacent pyramidal projection. That is, one pyramidal projectionis surrounded by other pyramidal projections, and the base of thepyramidal projection and the base of the adjacent pyramidal projectionhave a side in common.

Thus, since the pyramidal projections are arranged densely so that thetops thereof are evenly spaced, the display screen has a highanti-reflection function with which incident light from external can beefficiently scattered in many directions.

Since a plurality of the pyramidal projections 567, 597, and 529 of thisembodiment mode are arranged so that the tops thereof are evenly spaced,the cross sectional surfaces of the plurality of the pyramidalprojections 567, 597, and 529 have the same shape as shown in FIGS. 7A,7B, 13, 26A, and 26B. The plurality of the pyramidal projections 567,597, and 529 are arranged so as to be in contact with each other andeach side of the base of the pyramidal projection is in contact with oneside of the base of the adjacent pyramidal projection. Therefore, inthis embodiment mode, the plurality of pyramidal projections arearranged with no space therebetween and cover the display screen surfaceas shown in FIGS. 7A, 7B, 13, 26A, and 26B. A plane portion of thedisplay screen surface is not exposed by the plurality of pyramidalprojections and incident light from external is incident on slopedsurfaces of the plurality of pyramidal projections, so that reflectionof incident light from external on the plane portion can be reduced.

In this embodiment mode, the distance between the tops of the pluralityof pyramidal projections and the width of the base of the pyramidalprojection are preferably equal to or shorter than 350 nm, and theheight of each of the plurality of pyramidal projections is preferablyequal to or longer than 800 nm. The fill rate of bases of the pluralityof pyramidal projections per unit area of the surface of a displayscreen (the rate of the display screen which is filled (occupied)) isequal to or more than 80%, preferably equal to or more than 90%. A fillrate is a rate of a formation region of pyramidal projections over adisplay screen surface. When the fill rate is equal to or more than 80%,the rate of plane portions where no pyramidal projection is formed(which is parallel to the display screen) is equal to or less than 20%.The ratio of the height of a pyramidal projection to the width of a basethereof is preferably equal to or more than 5. Under the above-describedcondition, the rate of light incident from external on the plane portionis reduced and thus reflection with respect to the viewer side can beprevented.

Further, the plurality of pyramidal projections preferably have manymore sides having angles with respect to the bases thereof becauseincident light from external are scattered in many more directions. Inthis embodiment mode, a pyramidal projection has six sides which are incontact with and at an angle to a base. In addition, since the base of apyramidal projection shares a vertex with bases of other two pyramidalprojections and the pyramidal projection has a plurality of sides whichare provided at an angle, incident light is more easily reflected inmany directions. Therefore, the more vertices the base of a pyramidalprojection has, the more easily an anti-reflection function thereof canbe exerted, and the pyramidal projection has six vertices of the base.The pyramidal projections each having a hexagonal pyramidal base of thisembodiment mode have shapes capable of being densely arranged with nospace therebetween, which are optimal shapes each having the largestnumber of sides of any pyramidal projection and a high anti-reflectionfunction with which incident light can be scattered efficiently in manydirections.

The pyramidal projection can be formed of a material having a refractiveindex which is nonuniform and varies from the side surface toward adisplay screen. For example, in each of the plurality of pyramidalprojections, a portion closer to the side surface is formed of amaterial having a refractive index equivalent to that of the air toreduce reflection, by the side surface of the pyramidal projection, oflight incident on each pyramidal projection from external through theair. On the other hand, a portion of each of the plurality of pyramidalprojections, which is closer to the substrate on the display screenside, is formed of a material having a refractive index equivalent tothat of the substrate to further reduce reflection by an interfacebetween each pyramidal projection and the substrate, of incident lightfrom external which propagates inside each pyramidal projection and isincident on the substrate. Since the refractive index of air is smallerthan that of a glass substrate, when a glass substrate is used as thesubstrate, each pyramidal projection may have such a structure in whicha portion closer to the top of the pyramidal projection is formed of amaterial having a lower refractive index and a portion closer to thebase of the pyramidal projection is formed of a material having a higherrefractive index, so that the refractive index increases from the top tothe base of the pyramidal projection.

A material used for forming the pyramidal projection may beappropriately selected in accordance with a material of the substrateforming a display screen surface, such as silicon, nitrogen, fluorine,oxide, nitride, or fluoride. As the oxide, the following can be used:silicon oxide (SiO₂), boric oxide (B₂O₃), sodium oxide (NaO₂), magnesiumoxide (MgO), aluminum oxide (alumina) (Al₂O₃), potassium oxide (K₂O),calcium oxide (CaO), diarsenic trioxide (arsenious oxide) (As₂O₃),strontium oxide (SrO), antimony oxide (Sb₂O₃), barium oxide (BaO),indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO) inwhich indium oxide is mixed with zinc oxide (ZnO), a conductive materialin which indium oxide is mixed with silicon oxide (SiO₂), organicindium, organic tin, indium oxide containing tungsten oxide, indium zincoxide containing tungsten oxide, indium oxide containing titanium oxide,indium tin oxide containing titanium oxide, or the like. As the nitride,aluminum nitride (AlN), silicon nitride (SiN), or the like can be used.As the fluoride, lithium fluoride (LiF), sodium fluoride (NaF),magnesium fluoride (MgF₂), calcium fluoride (CaF₂), lanthanum fluoride(LaF₃), or the like can be used. The antireflective film may include oneor more kinds of the above-described silicon, nitrogen, fluorine, oxide,nitride, and fluoride. A mixing ratio thereof may be appropriately setin accordance with the ratio of components (a composition ratio) of thesubstrate.

The pyramidal projection can be formed in such a manner that a thin filmis formed by a sputtering method, a vacuum evaporation method, a PVD(physical vapor deposition) method, or a CVD (chemical vapor deposition)method such as a low-pressure CVD (LPCVD) method or a plasma CVD method,and then etched to have a desired shape. Alternatively, a dropletdischarging method by which a pattern can be selectively formed, aprinting method by which a pattern can be transferred or drawn (a methodfor forming a pattern such as screen printing or offset printing), acoating method such as a spin coating method, a dipping method, adispenser method, a brush coating method, a spraying method, a flowcoating method, or the like may be employed. Still alternatively, animprinting technique or a nanoimprinting technique with which ananoscale three-dimensional structure can be formed by a transfertechnology may be employed. Imprinting and nanoimprinting are techniqueswith which a minute three-dimensional structure can be formed withoutusing a photolithography process.

The display device of this embodiment mode has a plurality of pyramidalprojections on the surface thereof. Reflected incident light fromexternal is reflected to not the viewer side but another adjacentpyramidal projection because a side surface of each pyramidal projectionis not horizontal. Alternatively, reflected incident light propagatesbetween adjacent pyramidal projections. Incident light from external ispartly transmitted through a pyramidal projection, and the rest of theincident light from external, which is reflected light, is then incidenton an adjacent pyramidal projection. In this manner, the incident lightfrom external which is reflected by a side surface of the pyramidalprojection repeats incidence on adjacent pyramidal projections.

That is, the number of times that incident light from external isincident on the pyramidal projections, of the incident light fromexternal which is incident on the display device, is increased;therefore, the amount of light transmitted through the pyramidalprojections is increased. Thus, the amount of incident light fromexternal which is reflected to the viewer side is reduced, and the causeof a reduction in visibility such as reflection can be prevented.

This embodiment mode can provide a high-visibility display device havingan anti-reflection function with which reflection of incident light fromexternal can be further reduced by being provided with a plurality ofpyramidal projections on their surface. Accordingly, a more high-qualityand high-performance display device can be manufactured.

This embodiment mode can be freely combined with Embodiment Mode 1.

Embodiment Mode 4

In this embodiment mode, an example of a display device having ananti-reflection function with which reflection of incident light fromexternal can be further reduced, for the purpose of providing excellentvisibility, is described. Specifically, a liquid crystal display deviceusing a liquid crystal display element as a display element isdescribed.

FIG. 8A is a top plan view of a liquid crystal display device having aplurality of pyramidal projections, and FIG. 813 is a cross-sectionalview taken along line C-D in FIG. 8A. In the top plan view of FIG. 8A,the plurality of pyramidal projections are omitted.

As shown in FIG. 8A, a pixel region 606, a driver circuit region 608 awhich is a scan line driver circuit region, and a driver circuit region608 b which is a scan line driver circuit region are sealed between asubstrate 600 and a counter substrate 695 with a sealing material 692. Adriver circuit region 607 which is a signal line driver circuit formedwith a driver IC is provided over the substrate 600. A transistor 622and a capacitor 623 are provided in the pixel region 606. A drivercircuit having transistors 620 and 621 is provided in the driver circuitregion 608 b. An insulating substrate can be used as the substrate 600as in the above embodiment modes. Although there is a concern that asubstrate formed of a synthetic resin generally has a lower temperaturelimit than other substrates, the substrate formed of a synthetic resincan be used when a manufacturing process is performed using a substratewith high heat resistance and then the substrate formed of a syntheticresin displaces the substrate with high heat resistance.

In the pixel region 606, the transistor 622 which is to be a switchingelement is provided with base films 604 a and 604 b interposedtherebetween. In this embodiment mode, a multi-gate thin film transistor(TFT) is used as the transistor 622, which includes a semiconductorlayer having impurity regions serving as a source region and a drainregion, a gate insulting layer, a gate electrode layer having astacked-layer structure of two layers, a source electrode layer, and adrain electrode layer. The source electrode layer or drain electrodelayer is in contact with and electrically connected to an impurityregion of the semiconductor layer and a pixel electrode layer 630. Thethin film transistor can be manufactured by various methods. Forexample, a crystalline semiconductor film is used for an active layer, agate electrode is formed over the crystalline semiconductor film with agate insulating film interposed therebetween, and an impurity elementcan be added to the active layer with use of the gate electrode. Thus,when the gate electrode is used for adding the impurity element, a maskfor adding the impurity element is not necessarily formed. The gateelectrode can have a single-layer structure or a stacked-layerstructure. The impurity region can be a high-concentration impurityregion or a low-concentration impurity region with its concentrationbeing controlled. A structure of a thin film transistor having alow-concentration impurity region is called an LDD (light doped drain)structure. Alternatively, the low-concentration impurity region may beformed so as to overlap with the gate electrode and a structure of sucha thin film transistor is called a GOLD (gate overlapped LDD) structure.The polarity of the thin film transistor is an n type when phosphorus(P) or the like is used for the impurity region. The polarity of thethin film transistor is a p type when boron (B) or the like is added.After that, insulating films 611 and 612 covering the gate electrode andthe like are formed. A dangling bond of the crystalline semiconductorfilm can be terminated by a hydrogen element mixed into the insulatingfilm 611 (and the insulating film 612).

In order to further improve planarity, insulating films 615 and 616 maybe formed as interlayer insulating films. For the insulating films 615and 616, an organic material, an inorganic material, or a stacked-layerstructure thereof can be used. For example, a material selected fromsilicon oxide, silicon nitride, silicon oxynitride, silicon nitrideoxide, aluminum nitride, aluminum oxynitride, aluminum nitride oxidecontaining more nitrogen than oxygen, aluminum oxide, diamond-likecarbon (DLC), polysilazane, nitrogen-containing carbon (CN), PSG(phosphosilicate glass), BPSG (borophosphosilicate glass), alumina, andany other substance containing an inorganic insulating material can beused. Alternatively, an organic insulating material may be used. As theorganic insulating material, either a photosensitive material or anonphotosensitive material can be used, and polyimide, acrylic,polyamide, polyimide amide, resist, benzocyclobutene, a siloxane resin,or the like can be used. It is to be noted that a siloxane resin is aresin containing a Si—O—Si bond. The skeletal structure of siloxane isformed of a bond of silicon (Si) and oxygen (O). As a substituent, anorganic group containing at least hydrogen (such as an alkyl group oraromatic hydrocarbon) is used. Alternatively, a fluoro group or a fluorogroup and an organic group containing at least hydrogen may be used asthe substituent.

The pixel region and the driver circuit region can be formed over onesubstrate when the crystalline semiconductor film is used. In this case,a transistor in the pixel portion and a transistor in the driver circuitregion 608 b are formed at the same time. The transistor used in thedriver circuit region 608 b forms a CMOS circuit. Although a thin filmtransistor included in the CMOS circuit has a GOLD structure, it mayhave an LDD structure like the transistor 622.

A structure of the thin film transistor in the pixel region is notlimited to those in this embodiment mode, and a single-gate structure inwhich one channel formation region is formed, a double-gate structure inwhich two channel formation regions are formed, or a triple-gatestructure in which three channel formation regions are formed may beemployed. A thin film transistor in a peripheral driver circuit regionmay also have a single-gate structure, a double-gate structure, or atriple-gate structure.

It is to be noted that a method for manufacturing a thin film transistoris not limited to those described in this embodiment mode. The thin filmtransistor may have a top gate structure (such as a staggered type), abottom gate structure (such as a inverse staggered type), a dual gatestructure in which two gate electrode layers are arranged above or belowa channel region, each with a gate insulating film interposedtherebetween, or another structure.

Then, an insulating layer 631 called an alignment film is formed by aprinting method or a droplet discharging method so as to cover the pixelelectrode layer 630 and the insulating film 616. It is to be noted thatthe insulating layer 631 can be selectively formed by a screen printingmethod or an off-set printing method. Thereafter, rubbing treatment isperformed. This rubbing treatment is not performed in some cases when aliquid crystal mode is, for example, a VA mode. An insulating layer 633serving as an alignment film is similar to the insulating layer 631.Then, the sealing material 692 is formed in a peripheral region of thepixels by a droplet discharging method.

After that, the counter substrate 695 provided with the insulating layer633 serving as the alignment film, a conductive layer 634 serving as acounter electrode, a colored layer 635 serving as a color filter, apolarizer 641 (also referred to as a polarizing plate), and pyramidalprojections 642 is attached to the substrate 600 which is a TFTsubstrate with a spacer 637 interposed therebetween. A liquid crystallayer 632 is provided in a space therebetween. Since the liquid crystaldisplay device of this embodiment mode is a transmissive type, apolarizer (polarizing plate) 643 is also provided on the substrate 600side, which is opposite to a side where an element is formed. Thepolarizer can be provided over the substrate with the use of an adhesivelayer. A filler may be mixed into the sealing material, and a shieldingfilm (black matrix) or the like may be formed over the counter substrate695. It is to be noted that a color filter or the like may be formed ofmaterials which exhibit red (R), green (G), and blue (B) when the liquidcrystal display device performs full-color display, and the coloredlayer may be omitted or may be formed of a material which exhibits atleast one color when the liquid crystal display device performssingle-color display.

The display device of FIGS. 8A and 8B is an example in which theplurality of pyramidal projections 642 are provided on an outer side ofthe counter substrate 695, and the polarizer 641, the colored layer 635,and the conductive layer 634 are provided in this order on an innerside. However, the polarizer 641 may be provided on the outer side ofthe counter substrate 695 (on the viewer side), and in that case, theplurality of pyramidal projections may be provided on a surface of thepolarizer (polarizing plate). The stacked-layer structure of thepolarizer and the colored layer is also not limited to that of FIGS. 8Aand 8B and may be appropriately determined depending on materials of thepolarizer and the colored layer or conditions of a manufacturingprocess.

It is to be noted that when ROB light-emitting diodes (LEDs) or the likeare provided in a backlight and a field sequential method for performingcolor display by time division is employed, there is the case where acolor filter is not provided. The black matrix may be provided so as tooverlap with the transistor and the CMOS circuit because the blackmatrix reduces the reflection of incident light from external by thewiring in the transistor and the CMOS circuit. Alternatively, the blackmatrix may be provided so as to overlap with the capacitor. It isbecause the black matrix can prevent reflection due to a metal filmincluded in the capacitor.

As a method for forming the liquid crystal layer, a dispenser method(dripping method) or an injection method by which the substrate 600provided with an element and the counter substrate 695 are attached andthen a liquid crystal is injected with the use of capillary phenomenoncan be used. A dripping method may be employed when a large substrate towhich an injection method is difficult to be applied is used.

A spacer may be provided by a method by which particles each having asize of several μm are sprayed. In this embodiment mode, a method bywhich a resin film is formed over the entire surface of the substrateand then etched is employed. A material for the spacer is applied by aspinner and then, light exposure and developing treatment are performedto form a predetermined pattern. Further, the material is heated at 150to 200° C. in a clean oven or the like to be cured. The spacermanufactured in this manner can have various shapes depending on theconditions of light exposure and the developing treatment. It ispreferable that the spacer have a columnar shape with a flat top so thatmechanical strength of the liquid crystal display device can be securedwhen the counter substrate is attached. The shape of the spacer is notparticularly limited and may be conical, pyramidal, or the like.

Then, an FPC 694, which is a wiring board for connection, is providedover a terminal electrode layer 678 electrically connected to the pixelregion, with an anisotropic conductive layer 696 interposedtherebetween. The FPC 694 transmits a signal and a potential fromexternal. Through the aforementioned steps, a liquid crystal displaydevice having a display function can be manufactured.

The wiring and the gate electrode layer, which are included in thetransistor, the pixel electrode layer 630, and the conductive layer 634serving as the counter electrode layer can be formed using indium tinoxide (ITO), indium zinc oxide (IZO) in which zinc oxide (ZnO) is mixedwith indium oxide, a conductive material in which silicon oxide (SiO₂)is mixed with indium oxide, organic indium, organic tin, indium oxidecontaining tungsten oxide, indium zinc oxide containing tungsten oxide,indium oxide containing titanium oxide, indium tin oxide containingtitanium oxide; a metal such as tungsten (W), molybdenum (Mo), zirconium(Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium(Cr), cobalt (Co), nickel (Ni), titanium (Ti), platinum (Pt), aluminum(Al), copper (Cu), or silver (Ag); an alloy of such metals; or metalnitride thereof.

A retardation plate may be provided between the polarizing plate and theliquid crystal layer.

In this embodiment mode, the display device has the plurality ofpyramidal projections on the display screen surface provided with ananti-reflection function with which reflection of incident light fromexternal is prevented. In this embodiment mode, the pyramidalprojections 642 are provided on a surface of the counter substrate 695,which is on a display screen viewer side. In a case where the displayscreen has a plane with respect to incident light from external (a sideparallel to the display screen), incident light from external arereflected to the viewer side. Therefore, the display screen having fewerplane regions has a higher anti-reflection function. In order thatincident light from external are further scattered, a plurality of sideseach forming an angle with respect to a surface of the display screen ispreferably formed on the surface of the display screen.

In the present invention, since the plurality of pyramidal projectionsare geometrically densely arranged with no space therebetween, arefractive index varies from the display screen surface side to theoutside (the air) due to the physical shape of a pyramidal projection.In this embodiment mode, the tops of the plurality of pyramidalprojections are arranged so as to be evenly spaced and each side of thebase of a pyramidal projection is in contact with one side of the baseof an adjacent pyramidal projection. That is, one pyramidal projectionis surrounded by other pyramidal projections, and the base of thepyramidal projection and the base of the adjacent pyramidal projectionhave a side in common.

Thus, since the pyramidal projections are arranged densely so that thetops thereof are evenly spaced, the display screen has a highanti-reflection function with which incident light from external can beefficiently scattered in many directions.

Since a plurality of the pyramidal projections 642 of this embodimentmode are arranged so that the tops thereof are evenly spaced, the crosssectional surfaces of the plurality of the pyramidal projections 642have the same shape as shown in FIG. 8B. The plurality of the pyramidalprojections 642 are arranged so as to be in contact with each other andeach side of the base of the pyramidal projection is in contact with oneside of the base of the adjacent pyramidal projection. Therefore, inthis embodiment mode, the plurality of pyramidal projections arearranged with no space therebetween and cover the display screen surfaceas shown in FIG. 5B. A plane portion of the display screen surface isnot exposed by the plurality of pyramidal projections and incident lightfrom external is incident on sloped surfaces of the plurality ofpyramidal projections, so that reflection of incident light fromexternal on the plane portion can be reduced.

In this embodiment mode, the distance between the tops of the pluralityof pyramidal projections and the width of the base of the pyramidalprojection are preferably equal to or shorter than 350 nm, and theheight of each of the plurality of pyramidal projections is preferablyequal to or longer than 800 nm. The fill rate of bases of the pluralityof pyramidal projections per unit area of the surface of a displayscreen (the rate of the display screen which is filled (occupied)) isequal to or more than 80%, preferably equal to or more than 90%. A fillrate is a rate of a formation region of pyramidal projections over adisplay screen surface. When the fill rate is equal to or more than 80%,the rate of plane portions where no pyramidal projection is formed(which is parallel to the display screen) is equal to or less than 20%.The ratio of the height of a pyramidal projection to the width of a basethereof is equal to or more than 5. Under the above-described condition,the rate of light incident from external on the plane portion is reducedand thus reflection with respect to the viewer side can be prevented.

Further, the plurality of pyramidal projections preferably have manymore sides having angles with respect to the bases thereof becauseincident light from external are scattered in many more directions. Inthis embodiment mode, a pyramidal projection has six sides which are incontact with and at an angle to a base. In addition, since the base of apyramidal projection shares a vertex with bases of other two pyramidalprojections and the pyramidal projection has a plurality of sides whichare provided at an angle, incident light is more easily reflected inmany directions. Therefore, the more vertices the base of a pyramidalprojection has, the more easily an anti-reflection function thereof canbe exerted, and the pyramidal projection has six vertices of the base.The pyramidal projections each having a hexagonal pyramidal base of thisembodiment mode have shapes capable of being densely arranged with nospace therebetween, which are optimal shapes each having the largestnumber of sides of any pyramidal projection and a high anti-reflectionfunction with which incident light can be scattered efficiently in manydirections.

The display device of this embodiment mode is acceptable as long as ithas a structure having pyramidal projections which are densely arrangedso as to be adjacent to each other. A structure may be employed in whichpyramidal projections are formed directly into a surface part of asubstrate (film) forming the display screen, as an integrated continuousstructure. For example, a surface of a substrate (film) may be processedso that pyramidal projections are formed thereinto, or a shape withpyramidal projections may be selectively formed by a printing methodsuch as nanoimprinting. Alternatively, pyramidal projections may beformed on a substrate (film) in another step.

The plurality of pyramidal projections may be formed as an integratedcontinuous film, or may be densely arranged on a substrate.

The pyramidal projection can be formed of a material having a refractiveindex which is nonuniform and varies from the side surface toward adisplay screen. For example, in each of the plurality of pyramidalprojections, a portion closer to the side surface is formed of amaterial having a refractive index equivalent to that of the air toreduce reflection, by the side surface of the pyramidal projection, oflight incident on each pyramidal projection from external through theair. On the other hand, a portion of each of the plurality of pyramidalprojections, which is closer to the substrate on the display screenside, is formed of a material having a refractive index equivalent tothat of the substrate to further reduce reflection by an interfacebetween each pyramidal projection and the substrate, of incident lightfrom external which propagates inside each pyramidal projection and isincident on the substrate. Since the refractive index of air is smallerthan that of a glass substrate, when a glass substrate is used as thesubstrate, each pyramidal projection may have such a structure in whicha portion closer to the top of the pyramidal projection is formed of amaterial having a lower refractive index and a portion closer to thebase of the pyramidal projection is formed of a material having a higherrefractive index, so that the refractive index increases from the top tothe base of the pyramidal projection.

The display device of this embodiment mode has a plurality of pyramidalprojections on the surface thereof. Reflected incident light fromexternal is reflected to not the viewer side but another adjacentpyramidal projection because a side surface of each pyramidal projectionis not horizontal. Alternatively, reflected incident light propagatesbetween adjacent pyramidal projections. Incident light from external ispartly transmitted through a pyramidal projection, and the rest of theincident light from external, which is reflected light, is then incidenton an adjacent pyramidal projection. In this manner, the incident lightfrom external which is reflected by a side surface of the pyramidalprojection repeats incidence on adjacent pyramidal projections.

That is, the number of times that incident light from external isincident on the pyramidal projections, of the incident light fromexternal which is incident on the display device, is increased;therefore, the amount of light transmitted through the pyramidalprojections is increased. Thus, the amount of incident light fromexternal which is reflected to the viewer side is reduced, and the causeof a reduction in visibility such as reflection can be prevented.

This embodiment mode can provide a high-visibility display device havingan anti-reflection function with which reflection of incident light fromexternal can be further reduced by being provided with a plurality ofpyramidal projections on their surface. Accordingly, a more high-qualityand high-performance display device can be manufactured.

This embodiment mode can be freely combined with Embodiment Mode 1.

Embodiment Mode 5

In this embodiment mode, an example of a display device having ananti-reflection function with which reflection of incident light fromexternal can be further reduced, for the purpose of providing excellentvisibility, is described. Specifically, a light-emitting display deviceusing a light-emitting element as a display element is described. Amethod for manufacturing the display device in this embodiment mode isdescribed in detail with reference to FIGS. 9A, 9B, and 12.

Base films 101 a and 101 b are formed over a substrate 100 having aninsulating surface as base films. In this embodiment mode, the base film101 a with a thickness of 10 to 200 nm (preferably, 50 to 150 nm) isformed using a silicon nitride oxide film, and the base film 101 b witha thickness of 50 to 200 nm (preferably 100 to 150 nm) is stackedthereover using a silicon oxinitride film. In this embodiment mode, thebase films 101 a and 101 b are formed using a plasma CVD method.

For a material of the base film, an acrylic acid, a methacrylic acid, ora derivative thereof; a heat-resistant high molecule such as polyimide,aromatic polyamide, or polybenzimidazole; or a siloxane resin may beused. Other resin materials such as a vinyl resin, for example,polyvinyl alcohol or polyvinyl butyral, an epoxy resin, a phenol resin,a novolac resin, an acrylic resin, a melamine resin, and a urethaneresin may be used. Alternatively, an organic material such asbenzocyclobutene, parylene, fluorinated arylene ether, or polyimide, ora composition material containing water-soluble homopolymers andwater-soluble copolymers may be used. Further alternatively, an oxazoleresin such as photo-curable polybenzoxazole may be used.

The base films can be formed by a sputtering method, a PVD (physicalvapor deposition) method, or a CVD (chemical vapor deposition) methodsuch as a low-pressure CVD (LPCVD) method or a plasma CVD method.Alternatively, a droplet discharging method, a printing method (a methodfor forming a pattern such as screen printing or offset printing), acoating method such as a spin coating method, a dipping method, adispenser method, or the like may be employed.

As the substrate 100, a glass substrate, or a quartz substrate may beused. Alternatively, a plastic substrate having heat resistance whichcan withstand the processing temperature in this embodiment mode, or aflexible substrate such as a film may be used. As a plastic substrate, asubstrate made of PET (polyethylene terephthalate), PEN (polyethylenenaphthalate), or PES (polyethersulfone) can be used. As a flexiblesubstrate, a synthetic resin such as acrylic can be used. Since adisplay device manufactured in this embodiment mode has a structure inwhich light is extracted from the light-emitting element through thesubstrate 100, it is necessary for the substrate 100 to have alight-transmitting property.

As the base film, silicon oxide, silicon nitride, silicon oxynitride,silicon nitride oxide, or the like can be used, and either a singlelayer structure or a stacked-layer structure including two or threelayers may be employed.

Next, a semiconductor film is formed over the base film. Thesemiconductor film may be formed to a thickness of 25 to 200 nm(preferably, 30 to 150 nm) by various methods (such as a sputteringmethod, an LPCVD method, and a plasma CVD method). In this embodimentmode, it is preferable to use a crystalline semiconductor layer which isobtained by crystallization of an amorphous semiconductor film by laser.

The semiconductor film obtained as described above may be doped with aslight amount of an impurity element (boron or phosphorus) in order tocontrol a threshold voltage of a thin film transistor. Such doping withthe impurity element may be performed to the amorphous semiconductorfilm before the crystallization step. When the amorphous semiconductorfilm is doped with an impurity element and then subjected to heattreatment to be crystallized, activation of the impurity element canalso be performed. In addition, a defect caused in doping or the likecan be ameliorated.

Then, the crystalline semiconductor film is processed by etching into adesired shape, so that a semiconductor layer is formed.

Concerning an etching process, either plasma etching (dry etching) orwet etching may be employed. In the case of processing a largesubstrate, plasma etching is suitable. As an etching gas, afluorine-based gas such as CF₄ or NF₃ or a chlorine-based gas such asCl₂ or BCl₃ is used, and an inert gas such as He or Ar may be added tothe etching gas as appropriate. When an etching process using anatmospheric discharge is employed, local discharge process is alsopossible, and it is not necessary to form the mask layer over the entiresurface of the substrate.

In the present invention, a conductive layer for forming a wiring layeror an electrode layer, a mask layer for forming a predetermined pattern,or the like may be formed by a method by which a pattern can beselectively formed, such as a droplet discharging method. By a dropletdischarging (jetting) method (also called an ink-jet method depending onits system), a droplet of a composition which is mixed for a particularpurpose is selectively discharged (jetted) to form a predeterminedpattern (such as a conductive layer or an insulating layer). At thattime, treatment to control wettability or adhesion may be performed on aformation region. Alternatively, a method by which a pattern can betransferred or drawn, for example, a printing method (a method forforming a pattern, such as screen printing or offset printing), adispenser method, or the like may be used.

A mask used in this embodiment mode is formed using a resin materialsuch as an epoxy resin, an acrylic resin, a phenol resin, a novolacresin, a melamine resin, or a urethane resin. Alternatively, an organicmaterial such as benzocyclobutene, parylene, fluorinated arylene ether,or polyimide having a light-transmitting property; a compound materialmade by polymerization of a siloxane-based polymer or the like; acomposition material containing a water-soluble homopolymer and awater-soluble copolymer; or the like may be used. Still alternatively, acommercial resist material containing a photosensitizer may be used. Forexample, a positive type resist or a negative type resist may be used.In a case of using a droplet discharging method, even when using any ofthe above materials, a surface tension and a viscosity are appropriatelycontrolled by, for example, adjusting the concentration of a solvent oradding a surfactant or the like.

A gate insulating layer 107 which covers the semiconductor layer isformed. The gate insulating layer is formed using an insulating filmcontaining silicon to a thickness of 10 to 150 nm by a plasma CVDmethod, a sputtering method, or the like. The gate insulating layer maybe formed using a known material such as an oxide material or a nitridematerial of silicon, typified by silicon nitride, silicon oxide, siliconoxynitride, and silicon nitride oxide, and may be a stacked layer or asingle layer. The gate insulating layer may have a stacked-layerstructure of three layers including a silicon nitride film, a siliconoxide film, and a silicon nitride film, or a single-layer structure or astacked-layer structure of two layers of a silicon oxynitride film.

Next, a gate electrode layer is formed over the gate insulating layer107. The gate electrode layer can be formed by a sputtering method, anevaporation method, a CVD method, or the like. The gate electrode layermay be formed using an element selected from tantalum (Ta), tungsten(W), titanium (Ti), molybdenum (Mo), aluminum (Al), copper (Cu),chromium (Cr), and neodymium (Nd), or an alloy material or a compoundmaterial containing these elements as its main component. Alternatively,as the gate electrode layer, a semiconductor film typified by apolycrystalline silicon film doped with an impurity element such asphosphorus, or AgPdCu alloy may be used. The gate electrode layer mayhave a single-layer structure or a stacked-layer structure.

In this embodiment mode, the gate electrode layer is formed into atapered shape; however, the present invention is not limited thereto.The gate electrode layer may have a stacked layer structure, where onlyone layer has a tapered shape while the other is given a perpendicularside surface by anisotropic etching. The taper angles may differ betweenthe stacked gate electrode layers as in this embodiment mode or may bethe same. Due to the tapered shape, coverage by a film that is stackedthereover is improved and defects are reduced; therefore, reliability isenhanced.

The gate insulating layer 107 may be etched to some extent and reducedin thickness (so-called film reduction) by the etching step for formingthe gate electrode layer.

An impurity element is added to the semiconductor layer to form animpurity region. The impurity region can be formed as a highconcentration impurity region and a low concentration impurity region bythe control of the concentration of the impurity element. A thin filmtransistor having a low concentration impurity region is referred to asa thin film transistor having an LDD (light doped drain) structure. Inaddition, the low concentration impurity region can be formed so as tooverlap with the gate electrode. Such a thin film transistor is referredto as a thin film transistor having a GOLD (gate overlapped LDD)structure. The polarity of the thin film transistor is made to be an ntype by addition of phosphorus (P) or the like to an impurity regionthereof. In a case of forming a p-channel thin film transistor, boron(B) or the like may be added.

In this embodiment mode, a region of the impurity region, which overlapswith the gate electrode layer with the gate insulating layer interposedtherebetween, is denoted as an Lov region. Further, a region of theimpurity region, which does not overlap with the gate electrode layerwith the gate insulating layer interposed therebetween, is denoted as anLoff region. In FIG. 1513, the impurity regions are shown by hatchingand a blank. This does not mean that the blank is not doped with animpurity element but makes it easy to understand that the concentrationdistribution of the impurity element in the impurity regions reflectsthe mask and the doping condition. It is to be noted that this alsoapplies to other drawings in this specification.

In order to activate the impurity element, heat treatment, intense lightirradiation, or laser beam irradiation may be performed. At the sametime as the activation, plasma damage to the gate insulating layer andplasma damage to the interface between the gate insulating layer and thesemiconductor layer can be ameliorated.

Next, a first interlayer insulating layer covering the gate electrodelayer and the gate insulating layer is formed. In this embodiment mode,a stacked-layer structure of insulating films 167 and 168 is employed.As the insulating films 167 and 168, a silicon nitride film, a siliconnitride oxide film, a silicon oxynitride film, a silicon oxide film, orthe like can be formed by a sputtering method or a plasma CVD method.Alternatively, other insulating film containing silicon may be used as asingle layer or a stacked-layer structure including three or morelayers.

Further, heat treatment is performed at 300 to 550° C. for 1 to 12 hoursin a nitrogen atmosphere to hydrogenate the semiconductor layer.Preferably, this heat treatment is performed at 400 to 500° C. In thisstep, dangling bonds in the semiconductor layer are terminated byhydrogen contained in the insulating film 167 that is an interlayerinsulating layer. In this embodiment mode, heat treatment is performedat 410° C.

The insulating films 167 and 168 may be formed using a material selectedfrom aluminum nitride (AlN), aluminum oxynitride (AlON), aluminumnitride oxide containing more nitrogen than oxygen (AlNO), aluminumoxide, diamond-like carbon (DLC), nitrogen-containing carbon (CN),polysilazane, and other substances containing an inorganic insulatingmaterial. A material containing siloxane may be used. Alternatively, anorganic insulating material such as polyimide, acrylic, polyamide,polyimide amide, resist, or benzocyclobutene may be used. Furtheralternatively, an oxazole resin can be used, and for example,photo-curable polybenzoxazole or the like can be used.

Next, a contact hole (opening) is formed in the insulating film 167, theinsulating film 168, and the gate insulating layer 107 using a mask madeof a resist so as to reach the semiconductor layer. A conductive film isformed to cover the opening, and the conductive film is etched to form asource electrode layer or a drain electrode layer which is electricallyconnected to a part of a source region or a drain region. In order toform the source electrode layer or drain electrode layer, a conductivefilm is formed by a PVD method, a CVD method, an evaporation method, orthe like, and the conductive film is etched to have a desired shape.Then, a conductive layer can be selectively formed in a predeterminedposition by a droplet discharging method, a printing method, a dispensermethod, an electrolytic plating method, or the like, Alternatively, areflow method or a damascene method may be used. The source electrodelayer or drain electrode layer is formed using a metal such as Ag, Au,Cu, Ni, Pt, Pd, Ir, Rh, W, Al, Ta, Mo, Cd, Zn, Fe, Ti, Zr, or Ba; Si;Ge; or an alloy or metal nitride thereof. Alternatively, a stacked-layerstructure of these materials may be used.

Through the above steps, an active matrix substrate can be manufactured,in which a p-channel thin film transistor 285 having a p-type impurityregion in an Lov region and an n-channel thin film transistor 275 havingan n-channel impurity region in an Lov region are provided in aperipheral driver circuit region 204; and a multi-channel type n-channelthin film transistor 265 having an n-type impurity region in an Loffregion and a p-channel thin film transistor 245 having a p-type impurityregion in an Lov region are provided in a pixel region 206.

The structure of the thin film transistor is not limited to that of thisembodiment mode. A single-gate structure in which one channel formationregion is formed, a double-gate structure in which two channel formationregions are formed, or a triple-gate structure in which three channelformation regions are formed may be employed. Further, the thin filmtransistor in the peripheral driver circuit region may also employ asingle gate structure, a double gate structure, or a triple gatestructure.

Next, an insulating film 181 is formed as a second interlayer insulatinglayer. In FIGS. 9A and 9B, a separation region 201 for separation byscribing, an external terminal connection region 202 to which an FPC isattached, a wiring region 203 that is a lead wiring region for theperipheral portion, the peripheral driver circuit region 204, and thepixel region 206 are provided. Wirings 179 a and 179 b are provided inthe wiring region 203, and a terminal electrode layer 178 connected toan external terminal is provided in the external terminal connectionregion 202.

The insulating film 181 can be formed using a material selected fromsilicon oxide, silicon nitride, silicon oxynitride, silicon nitrideoxide, aluminum nitride (AlN), aluminum oxide containing nitrogen (alsoreferred to as aluminum oxynitride) (AlON), aluminum nitride containingoxygen (also referred to as aluminum nitride oxide) (AlNO), aluminiumoxide, diamond-like carbon (DLC), nitrogen-containing carbon (CN), PSG(phosphosilicate glass), BPSG (borophosphosilicate glass), alumina, andany other substance containing an inorganic insulating material. Asiloxane resin may also be used. Alternatively, an organic insulatingmaterial which is photosensitive or non-photosensitive such aspolyimide, acrylic, polyamide, polyimide amide, resist,benzocyclobutene, polysilazane, or any other low-dielectric constantmaterial may be used. Further alternatively, an oxazole resin may beused. For example, photo-curable polybenzoxazole or the like may beused. It is necessary that an interlayer insulating layer provided forplanarization have high heat resistance, a high insulating property, anda high level of planarity. Thus, the insulating film 181 is preferablyformed by a coating method typified by a spin coating method.

The insulating film 181 can be formed by a dipping method, spraycoating, a doctor knife, a roll coater, a curtain coater, a knifecoater, a CVD method, an evaporation method, or the like. Instead, theinsulating film 181 may be formed by a droplet discharging method. Inthe case of a droplet discharging method, a material solution can beeconomized on. Alternatively, a method by which a pattern can betransferred or drawn, like a droplet discharging method, for example, aprinting method (a method for forming a pattern, such as screen printingor offset printing), a dispenser method, or the like may be used.

A minute opening, that is, a contact hole, is formed in the insulatingfilm 181 in the pixel region 206.

Next, a first electrode layer (also referred to as pixel electrodelayer) 185 is formed so as to be in contact with a source electrodelayer or a drain electrode layer. The first electrode layer 185functions as an anode or a cathode and may be formed from a film mainlycontaining an element selected from Ti, Ni, W, Cr, Pt, Zn, Sn, In, andMo, or an alloy material or a compound material containing the aboveelement as its main component, such as titanium nitride, TiSi_(X)N_(Y),WSi_(X), tungsten nitride, WSi_(X)N_(Y), or NbN; or a stacked filmthereof with a total thickness of 100 to 800 nm.

In this embodiment mode, a light-emitting element is used as a displayelement, and the first electrode layer 185 has a light-transmittingproperty so that light from the light-emitting element is extracted fromthe first electrode layer 185 side. The first electrode layer 185 isformed using a transparent conductive film which is etched into adesired shape.

In the present invention, the first electrode layer 185 that is alight-transmitting electrode layer may be specifically formed using atransparent conductive film formed of a light-transmitting conductivematerial, and indium oxide containing tungsten oxide, indium zinc oxidecontaining tungsten oxide, indium oxide containing titanium oxide,indium tin oxide containing titanium oxide, or the like can be used. Itis needless to say that indium tin oxide (ITO), indium zinc oxide (IZO),indium tin oxide added with silicon oxide (ITSO), or the like may beused instead.

In addition, even in the case of a material that does not have alight-transmitting property, such as a metal film, when the thickness ismade thin (preferably, approximately 5 to 30 nm) so that light can betransmitted, light can be emitted through the first electrode layer 185.As a metal thin film that can be used for the first electrode layer 185,a conductive film formed of titanium, tungsten, nickel, gold, platinum,silver, aluminum, magnesium, calcium, lithium, or alloy thereof or thelike can be used.

The first electrode layer 185 can be formed by an evaporation method, asputtering method, a CVD method, a printing method, a dispenser method,a droplet discharging method, or the like. In this embodiment mode, thefirst electrode layer 185 is formed by a sputtering method using indiumzinc oxide containing tungsten oxide. The first electrode layer 185 ispreferably formed to a total thickness of 100 to 800 nm.

The first electrode layer 126 may be cleaned and polished by a CMPmethod or with the use of a polyvinyl alcohol-based porous material sothat the surface thereof is planarized. In addition, after beingpolished using a CMP method, the surface of the first electrode layer126 may be subjected to ultraviolet light irradiation, oxygen plasmatreatment, or the like.

Heat treatment may be performed after the first electrode layer 185 isformed. By the heat treatment, moisture contained in the first electrodelayer 185 is discharged. Accordingly, degassing or the like does notoccur in the first electrode layer 185. Thus, even when a light-emittingmaterial that easily deteriorates due to moisture is formed over thefirst electrode layer, the light-emitting material does not deteriorate.Therefore, a highly reliable display device can be manufactured.

Next, an insulating layer 186 (also referred to as a partition or abarrier) covering the edge of the first electrode layer 185 and thesource electrode layer or drain electrode layer is formed.

The insulating layer 186 may be formed using silicon oxide, siliconnitride, silicon oxynitride, silicon nitride oxide, or the like and hasa single layer structure or a stacked-layer structure of two or threelayers. Alternatively, the insulating layer 186 may be formed using amaterial selected from aluminum nitride, aluminum oxynitride containingmore oxygen than nitrogen, aluminum nitride oxide containing morenitrogen than oxygen, aluminum oxide, diamond-like carbon (DLC),nitrogen-containing carbon, polysilazane, and any other substancecontaining an inorganic insulating material. A material containingsiloxane may be used. Alternatively, an organic insulating materialwhich is photosensitive or non-photosensitive such as polyimide,acrylic, polyamide, polyimide amide, resist, or benzocyclobutene may beused. Further alternatively, an oxazole resin can be used. For example,photo-curable polybenzoxazole or the like can be used.

The insulating layer 186 can be formed by a sputtering method, a PVD(physical vapor deposition) method, a CVD (chemical vapor deposition)method such as a low-pressure CVD (LPCVD) method or a plasma CVD method,or the like. Alternatively, a droplet discharging method by which apattern can be selectively formed, a printing method by which a patterncan be transferred or drawn (a method for forming a pattern, such asscreen printing or offset printing), a dispenser method, a coatingmethod such as a spin-coating method, a dipping method, or the like maybe used.

As for an etching process for the processing into desired shapes, eitherplasma etching (dry etching) or wet etching may be employed. In the caseof processing a large substrate, plasma etching is suitable. As anetching gas, a fluorine-based gas such as CF₄ or NF₃ or a chlorine-basedgas such as Cl₂ or BCl₃ is used. An inert gas such as He or Ar may beadded to the etching gas as appropriate. When an etching process usingan atmospheric discharge is employed, local electric discharging processis also possible, and it is not necessary to form the mask layer overthe entire surface of the substrate.

In FIG. 9A, a wiring layer formed of the same material and in the samestep as a second electrode layer is electrically connected to a wiringlayer formed of the same material and in the same step as the gateelectrode layer.

A light-emitting layer 188 is formed over the first electrode layer 185.Although only one pixel is shown in FIGS. 9A and 9B, electroluminescentlayers corresponding to R (red), G (green) and B (blue) are formedseparately in this embodiment mode.

Then, a second electrode layer 189 formed of a conductive film isprovided over the light-emitting layer 188. As the second electrodelayer 189, Al, Ag, Li, Ca, or an alloy or a compound thereof such asMgAg, Mgln, AlLi, or CaF₂, or calcium nitride may be used. Thus, alight-emitting element 190 including the first electrode layer 185, thelight-emitting layer 188, and the second electrode layer 189 is formed(see FIG. 9B).

In the display device of this embodiment mode shown in FIGS. 9A and 9B,light from the light-emitting element 190 is emitted through the firstelectrode layer 185 side and transmitted in a direction indicated by thearrow in FIG. 9B.

In this embodiment mode, an insulating layer may be provided as apassivation film (protective film) over the second electrode layer 189.It is effective to provide a passivation film in this manner so as tocover the second electrode layer 189. The passivation film may be formedusing an insulating film containing silicon nitride, silicon oxide,silicon oxynitride, silicon nitride oxide, aluminum nitride, aluminumoxynitride, aluminum nitride oxide containing more nitrogen than oxygen,aluminum oxide, diamond-like carbon (DLC), or nitrogen-containingcarbon, and the insulating film can have a single-layer structure or astacked-layer structure. Alternatively, a siloxane resin may be used.

In that case, it is preferable to use a film by which favorable coverageis provided as the passivation film, and it is effective to use a carbonfilm, particularly, a DLC film as the passivation film. A DLC film canbe formed in the range from room temperature to 100° C.; therefore, itcan also be formed easily over the light-emitting layer 188 with lowheat resistance. A DLC film can be formed by a plasma CVD method(typically, an RF plasma CVD method, a microwave CVD method, an electroncyclotron resonance (ECR) CVD method, a thermal-filament CVD method, orthe like), a combustion flame method, a sputtering method, an ion beamevaporation method, a laser evaporation method, or the like. As areaction gas for deposition, a hydrogen gas and a hydrocarbon-based gas(for example, CH₄, C₂H₂, C₆H₆, and the like) are used to be ionized byglow discharge, and the ions are accelerated to impact against a cathodeto which negative self bias is applied. Further, a CN film may be formedwith the use of a C₂H₄ gas and a N₂ gas as a reaction gas. A DLC filmhas a high blocking effect against oxygen; therefore, oxidization of thelight-emitting layer 188 can be suppressed. Accordingly, a problem suchas oxidation of the light-emitting layer 188 during a sealing step whichis subsequently performed can be prevented.

The substrate 100 over which the light-emitting element 190 is formedand a sealing substrate 195 are firmly attached to each other with asealing material 192, so that the light-emitting element is filled andsealed (see FIGS. 9A and 9B). As the sealing material 192, typically, avisible light curable resin, an ultraviolet curable resin, or athermosetting resin is preferably used. For example, a bisphenol-Aliquid resin, a bisphenol-A solid resin, a bromine-containing epoxyresin, a bisphenol-F resin, a bisphenol-AD resin, a phenol resin, acresol resin, a novolac resin, a cycloaliphatic epoxy resin, an Epi-Bisepoxy resin, a glycidyl ester resin, a glycidyl amine-based resin, aheterocyclic epoxy resin, a modified epoxy resin, or the like can beused. It is to be noted that a region surrounded by the sealing materialmay be filled with a filler 193, and sealing may be performed in anitrogen atmosphere to fill the space between the substrate withnitrogen or the like. Since a bottom emission type is employed in thisembodiment mode, it is not necessary for the filler 193 to have alight-transmitting property. However, in the case where light isextracted through the filler 193, it is necessary for the filler to havea light-transmitting property. Typically, a visible light curable epoxyresin, an ultraviolet curable epoxy resin, or a thermosetting epoxyresin may be used. Through the aforementioned steps, a display devicehaving a display function using the light-emitting element of thisembodiment mode is completed. Further, the filler may be dripped in aliquid state to fill the display device. In the case of using ahygroscopic substance such as a drying agent as the filler, a furthermoisture absorption effect can be obtained. Therefore, deterioration ofthe element can be prevented.

A drying agent is provided in an EL display panel to preventdeterioration due to moisture in the element. In this embodiment mode,the drying agent is provided in a concave portion that is formed on thesealing substrate so as to surround the pixel region and thus, a thindesign is not spoiled. Further, since the drying agent is also formed ina region corresponding to a gate wiring layer so that a moistureabsorbing area is increased, moisture can be effectively absorbed. Inaddition, since the drying agent is formed over a gate wiring layerwhich is not self-emitting, light extraction efficiency is notdecreased.

The light-emitting element is sealed by a glass substrate in thisembodiment mode. It is to be noted that sealing treatment is treatmentfor protecting a light-emitting element from moisture, and any of amethod for mechanically sealing the light-emitting element by a covermaterial, a method for sealing the light-emitting element with athermosetting resin or an ultraviolet light curable resin, and a methodfor sealing the light-emitting element by a thin film having a highbarrier property such as a metal oxide film or a metal nitride film isused. As the cover material, glass, ceramics, plastics, or metal can beused, and it is necessary to use a material having a light-transmittingproperty in the case where light is emitted to the cover material side.The cover material and the substrate over which the light-emittingelement is formed are attached to each other with a sealing materialsuch as a thermosetting resin or an ultraviolet curable resin, and theresin is cured by heat treatment or ultraviolet light irradiationtreatment to form a sealed space. It is also effective to provide amoisture absorbing material typified by barium oxide in this sealedspace, This moisture absorbing material may be provided on and be incontact with the sealing material, or may be provided over or in theperiphery of the partition so as not to shield light from thelight-emitting element. Further, the space between the cover materialand the substrate over which the light-emitting element is formed can befilled with a thermosetting resin or an ultraviolet light curable resin.In this case, it is effective to add a moisture absorbing materialtypified by barium oxide in the thermosetting resin or the ultravioletlight curable resin.

FIG. 12 shows an example in which the source electrode layer or thedrain electrode layer is connected to the first electrode layer througha wiring layer so as to be electrically connected instead of beingdirectly in contact with each other, in the display device of FIGS. 9Aand 9B manufactured in this embodiment mode. In the display device shownin FIG. 12, the source electrode layer or the drain electrode layer ofthe thin film transistor which drives the light-emitting element iselectrically connected to a first electrode layer 395 through a wiringlayer 199. Moreover, in FIG. 12, the first electrode layer 395 ispartially stacked over the wiring layer 199; however, the firstelectrode layer 395 may be formed first and then the wiring layer 199may be formed on the first electrode layer 395.

In this embodiment mode, the terminal electrode layer 178 is connectedto an FPC 194 with an anisotropic conductive layer 196 interposedtherebetween in the external terminal connection region 202, and iselectrically connected to an external portion. In addition, as shown inFIG. 15A, which is a top plan view of the display device, the displaydevice manufactured in this embodiment mode includes a peripheral drivercircuit region 207 and a peripheral driver circuit region 208 eachincluding a scan line driver circuit in addition to the peripheraldriver circuit region 204 and the peripheral driver circuit region 209each including a signal line driver circuit.

A circuit such as that described above is formed in this embodimentmode; however, the present invention is not limited thereto. An IC chipmay be mounted by the aforementioned COG method or TAB method as theperipheral driver circuit. Further, one or a plurality of gate linedriver circuits and source line driver circuits may be provided.

In the display device of the present invention, there is no particularlimitation on a driving method for image display, and for example, a dotsequential driving method, a line sequential driving method, a framesequential driving method, or the like may be used. Typically, a linesequential driving method may be used, and a time division gray scaledriving method and an area gray scale driving method may be used asappropriate. Further, a video signal which is inputted to the sourceline of the display device may be an analog signal or a digital signal.The driver circuit and the like may be appropriately designed inaccordance with the video signal.

Since each of the display devices shown in FIGS. 9A and 9B and FIG. 12has a bottom-emission structure, light is emitted through the substrate100. Therefore, the viewer side is on the substrate 100 side. Thus, alight-transmitting substrate is used as the substrate 100, and pyramidalprojections 177 are provided on an outer side that corresponds to theviewer side.

The display device of this embodiment mode is acceptable as long as ithas a structure having pyramidal projections which are densely arrangedso as to be adjacent to each other. A structure may be employed in whichpyramidal projections are formed directly into a surface part of asubstrate (film) forming the display screen, as an integrated continuousstructure. For example, a surface of a substrate (film) may be processedso that pyramidal projections are formed thereinto, or a shape withpyramidal projections may be selectively formed by a printing methodsuch as nanoimprinting. Alternatively, pyramidal projections may beformed on a substrate (film) in another step.

The plurality of pyramidal projections may be formed as an integratedcontinuous film, or may be densely arranged on a substrate.

In this embodiment mode, the display device has the plurality ofpyramidal projections on the display screen surface provided with ananti-reflection function with which reflection of incident light fromexternal is prevented. In a case where the display screen has a planewith respect to incident light from external (a side parallel to thedisplay screen), incident light from external are reflected to theviewer side. Therefore, the display screen having fewer plane regionshas a higher anti-reflection function. In order that incident light fromexternal are further scattered, a plurality of sides each forming anangle with respect to a surface of the display screen is preferablyformed on the surface of the display screen.

In the present invention, since the plurality of pyramidal projectionsare geometrically densely arranged with no space therebetween, arefractive index varies from the display screen surface side to theoutside (the air) due to the physical shape of a pyramidal projection.In this embodiment mode, the tops of the plurality of pyramidalprojections are arranged so as to be evenly spaced and each side of thebase of a pyramidal projection is in contact with one side of the baseof an adjacent pyramidal projection. That is, one pyramidal projectionis surrounded by other pyramidal projections, and the base of thepyramidal projection and the base of the adjacent pyramidal projectionhave a side in common.

Thus, since the pyramidal projections are arranged densely so that thetops thereof are evenly spaced, the display screen has a highanti-reflection function with which incident light from external can beefficiently scattered in many directions.

Since a plurality of the pyramidal projections 177 of this embodimentmode are arranged so that the tops thereof are evenly spaced, the crosssectional surfaces of the plurality of the pyramidal projections 177have the same shape as shown in FIGS. 9A, 9B, and 12. The plurality ofthe pyramidal projections 177 are arranged so as to be in contact witheach other and each side of the base of the pyramidal projection is incontact with one side of the base of the adjacent pyramidal projection.Therefore, in this embodiment mode, the plurality of pyramidalprojections are arranged with no space therebetween and cover thedisplay screen surface as shown in FIGS. 9A, 9B, and 12. A plane portionof the display screen surface is not exposed by the plurality ofpyramidal projections and incident light from external is incident onsloped surfaces of the plurality of pyramidal projections, so thatreflection of incident light from external on the plane portion can bereduced.

In this embodiment mode, the distance between the tops of the pluralityof pyramidal projections and the width of the base of the pyramidalprojection are preferably equal to or shorter than 350 nm, and theheight of each of the plurality of pyramidal projections is preferablyequal to or longer than 800 nm. The fill rate of bases of the pluralityof pyramidal projections per unit area of the surface of a displayscreen (the rate of the display screen which is filled (occupied)) isequal to or more than 80%, preferably equal to or more than 90%. A fillrate is a rate of a formation region of pyramidal projections over adisplay screen surface. When the fill rate is equal to or more than 80%,the rate of plane portions where no pyramidal projection is formed(which is parallel to the display screen) is equal to or less than 20%.The ratio of the height of a pyramidal projection to the width of a basethereof is equal to or more than 5. Under the above-described condition,the rate of light incident from external on the plane portion is reducedand thus reflection with respect to the viewer side can be prevented.

Further, the plurality of pyramidal projections preferably have manymore sides having angles with respect to the bases thereof becauseincident light from external are scattered in many more directions. Inthis embodiment mode, a pyramidal projection has six sides which are incontact with and at an angle to a base. In addition, since the base of apyramidal projection shares a vertex with bases of other two pyramidalprojections and the pyramidal projection has a plurality of sides whichare provided at an angle, incident light is more easily reflected inmany directions. Therefore, the more vertices the base of a pyramidalprojection has, the more easily an anti-reflection function thereof canbe exerted, and the pyramidal projection has six vertices of the base.The pyramidal projections each having a hexagonal pyramidal base of thisembodiment mode have shapes capable of being densely arranged with nospace therebetween, which are optimal shapes each having the largestnumber of sides of any pyramidal projection and a high anti-reflectionfunction with which incident light can be scattered efficiently in manydirections.

Since the plurality of pyramidal projections 177 of this embodiment modeare arranged so that the tops thereof are evenly spaced, isoscelestriangles having the same shapes are adjacent to each other in crosssection.

The display device of this embodiment mode has a plurality of pyramidalprojections on the surface thereof. Reflected incident light fromexternal is reflected to not the viewer side but another adjacentpyramidal projection because a side surface of each pyramidal projectionis not horizontal. Alternatively, reflected incident light propagatesbetween adjacent pyramidal projections. Incident light from external ispartly transmitted through a pyramidal projection, and the rest of theincident light from external, which is reflected light, is then incidenton an adjacent pyramidal projection. In this manner, the incident lightfrom external which is reflected by a side surface of the pyramidalprojection repeats incidence on adjacent pyramidal projections.

That is, the number of times that incident light from external isincident on the pyramidal projections, of the incident light fromexternal which is incident on the display device, is increased;therefore, the amount of light transmitted through the pyramidalprojections is increased. Thus, the amount of light from externalreflected to the viewer side is reduced, and the cause of a reduction invisibility such as reflection can be prevented.

This embodiment mode can provide a high-visibility display device havingan antireflection function with which reflection of incident light fromexternal can be further reduced by being provided with a plurality ofpyramidal projections on their surface. Accordingly, a more high-qualityand high-performance display device can be manufactured.

This embodiment mode can be freely combined with Embodiment Mode 1.

Embodiment Mode 6

By applying the present invention, a display device having alight-emitting element can be formed. Note that light is emitted fromthe light-emitting element in the following manner: bottom emission, topemission, or dual emission. In this embodiment mode, examples of dualemission and top emission are described with reference to FIGS. 10 and11.

A display device shown in FIG. 11 includes an element substrate 1600, athin film transistor 1655, a thin film transistor 1665, a thin filmtransistor 1675, a thin film transistor 1685, a first electrode layer1617, an electroluminescent layer 1619, a second electrode layer 1620, afiller 1622, a sealing material 1632, an insulating film 1601 a, aninsulating film 1601 b, a gate insulating layer 1610, an insulating film1611, an insulating film 1612, an insulating layer 1614, a sealingsubstrate 1625, a wiring layer 1633, a terminal electrode layer 1681, ananisotropic conductive layer 1682, an FPC 1683, and pyramidalprojections 1627 a and 1627 b. The display device also includes anexternal terminal connection region 232, a sealing region 233, aperipheral driver circuit region 234, and a pixel region 236. The filler1622 can be formed by a dropping method using a composition in a liquidstate. A light-emitting display device is sealed by attaching theelement substrate 1600 provided with the filler by a dropping method andthe sealing substrate 1625 to each other.

The display device shown in FIG. 11 has a dual-emission structure, inwhich light is emitted through both the element substrate 1600 and thesealing substrate 1625 in directions of arrows. Therefore,light-transmitting electrode layers are used as the first electrodelayer 1617 and the second electrode layer 1620.

In this embodiment mode, the first electrode layer 1617 and the secondelectrode layer 1620 which are light-transmitting electrode layers maybe specifically formed using a transparent conductive film formed of alight-transmitting conductive material, and indium oxide containingtungsten oxide, indium zinc oxide containing tungsten oxide, indiumoxide containing titanium oxide, indium tin oxide containing titaniumoxide, or the like can be used It is needless to say that indium tinoxide (ITO), indium zinc oxide (IZO), indium tin oxide added withsilicon oxide (ITSO), or the like may be used instead.

In addition, even in the case of a material that does not have alight-transmitting property, such as a metal film, when the thickness ismade thin (preferably, approximately 5 to 30 nm) so that light can betransmitted, light can be emitted through the first electrode layer 1617and the second electrode layer 1620. As a metal thin film that can beused for the first electrode layer 1617 and the second electrode layer1620, a conductive film formed of titanium, tungsten, nickel, gold,platinum, silver, aluminum, magnesium, calcium, lithium, or alloythereof, or the like can be used.

As described above, the display device of FIG. 11 has a structure inwhich light emitted from a light-emitting element 1605 is emitted fromboth sides through both the first electrode layer 1617 and the secondelectrode layer 1620.

A display device of FIG. 10 has a structure for top emission in adirection of an arrow. The display device shown in FIG. 10 includes anelement substrate 1300, a thin film transistor 1355, a thin filmtransistor 1365, a thin film transistor 1375, a thin film transistor1385, a wiring layer 1324, a first electrode layer 1317, anelectroluminescent layer 1319, a second electrode layer 1320, aprotective film 1321, a filler 1322, a sealing material 1332, aninsulating film 1301 a, an insulating film 1301 b, a gate insulatinglayer 1310, an insulating film 1311, an insulating film 1312, aninsulating layer 1314, a sealing substrate 1325, a wiring layer 1333, aterminal electrode layer 1381, an anisotropic conductive layer 1382, andan FPC 1383.

In each of the display devices in FIGS. 10 and 11, an insulating layerstacked over the terminal electrode layer is removed by etching. Whenthe display device has a structure in which an insulating layer havingmoisture permeability is not provided in the vicinity of a terminalelectrode layer, reliability is improved. The display device of FIG. 10includes an external terminal connection region 232, a sealing region233, a peripheral driver circuit region 234, and a pixel region 236. Inthe display device of FIG. 10, the wiring layer 1324 that is a metallayer having reflectivity is formed below the first electrode layer 1317in the display device having a dual emission structure shown in FIG. 1.The first electrode layer 1317 that is a transparent conductive film isformed over the wiring layer 1324. Since it is acceptable as long as thewiring layer 1324 has reflectivity, the wiring layer 1324 may be formedusing a conductive film made of titanium, tungsten, nickel, gold,platinum, silver, copper, tantalum, molybdenum, aluminum, magnesium,calcium, lithium, or an alloy thereof. It is preferable to use asubstance having reflectivity in a visible light range, and a titaniumnitride film is used in this embodiment mode. In addition, the firstelectrode layer 1317 may be formed using a conductive film, and in thatcase, the wiring layer 1324 having reflectivity may be omitted.

The first electrode layer 1317 and the second electrode layer 1320 maybe specifically formed using a transparent conductive film formed of alight-transmitting conductive material, and indium oxide containingtungsten oxide, indium zinc oxide containing tungsten oxide, indiumoxide containing titanium oxide, indium tin oxide containing titaniumoxide, or the like can be used. It is needless to say that indium tinoxide (ITO), indium zinc oxide (IZO), indium tin oxide added withsilicon oxide (ITSO), or the like may be used instead.

Even in the case of a material that does not have a light-transmittingproperty, such as a metal film, when the thickness is made thinpreferably, approximately 5 to 30 nm) so that light can be transmitted,light can be emitted through the second electrode layer 1320. As a metalthin film that can be used for the second electrode layer 1320, aconductive film formed of titanium, tungsten, nickel, gold, platinum,silver, aluminum, magnesium, calcium, lithium, or an alloy thereof, orthe like can be used.

A pixel of a display device which is formed using a light-emittingelement can be driven by a simple matrix mode or an active matrix mode.In addition, either digital driving or analog driving can be applied.

A color filter (colored layer) may be formed over a sealing substrate.The color filter (colored layer) can be formed by an evaporation methodor a droplet discharging method. High-definition display can beperformed with the use of the color filter (colored layer). This isbecause a broad peak can be modified to be sharp in an emission spectrumof each of R, G, and B by the color filter (colored layer).

A material emitting light of a single color is formed and it is combinedwith a color filter or a color conversion layer, so that full colordisplay can be performed. The color filter (colored layer) or the colorconversion layer may be formed over, for example, the sealing substrateand attached to an element substrate.

It is needless to say that display of a single color emission may beperformed. For example, an area color type display device may be formedusing single color emission. The area color type display device issuitable for a passive matrix display portion and can mainly displaycharacters and symbols.

Since the display device shown in FIG. 11 has a dual-emission structure,light is emitted through both the element substrate 1600 and the sealingsubstrate 1625. Therefore, the viewer side is on each of the elementsubstrate 1600 side and the sealing substrate 1625 side. Thus, alight-transmitting substrate is used as each of the element substrate1600 and the sealing substrate 1625, and the pyramidal projections 1627a and 627 b are provided on respective outer sides that correspond toviewer sides. On the other hand, since the display device shown in FIG.10 has a top-emission structure, the sealing substrate 1325 on theviewer side is a light-transmitting substrate. Pyramidal projections1327 are provided on an outer side thereof.

The display device of this embodiment mode is acceptable as long as ithas a structure having pyramidal projections which are densely arrangedso as to be adjacent to each other. A structure may be employed in whichpyramidal projections are formed directly into a surface part of asubstrate (film) forming the display screen, as an integrated continuousstructure. For example, a surface of a substrate (film) may be processedso that pyramidal projections are formed thereinto, or a shape withpyramidal projections may be selectively formed by a printing methodsuch as nanoimprinting. Alternatively, pyramidal projections may beformed on a substrate (film) in another step.

The plurality of pyramidal projections may be formed as an integratedcontinuous film, or may be densely arranged on a substrate.Alternatively, pyramidal projections may be formed into a substrate inadvance. FIG. 10 is an example in which a plurality of pyramidalprojections 1327 are provided on a surface of a substrate 1325 as anintegrated continuous structure.

In this embodiment mode, the display device has the plurality ofpyramidal projections on the display screen surface provided with ananti-reflection function with which reflection of incident light fromexternal is prevented. In a case where the display screen has a planewith respect to incident light from external (a side parallel to thedisplay screen), incident light from external are reflected to theviewer side. Therefore, the display screen having fewer plane regionshas a higher anti-reflection function. In order that incident light fromexternal are further scattered, a plurality of sides each forming anangle with respect to a surface of the display screen is preferablyformed on the surface of the display screen.

In the present invention, since the plurality of pyramidal projectionsare geometrically densely arranged with no space therebetween, arefractive index varies from the display screen surface side to theoutside (the air) due to the physical shape of a pyramidal projection.In this embodiment mode, the tops of the plurality of pyramidalprojections are arranged so as to be evenly spaced and each side of thebase of a pyramidal projection is in contact with one side of the baseof an adjacent pyramidal projection. That is, one pyramidal projectionis surrounded by other pyramidal projections, and the base of thepyramidal projection and the base of the adjacent pyramidal projectionhave a side in common.

Thus, since the pyramidal projections are arranged densely so that thetops thereof are evenly spaced, the display screen has a highanti-reflection function with which incident light from external can beefficiently scattered in many directions.

Since a plurality of the pyramidal projections 1327, 1627 a, and 1627 bof this embodiment mode are arranged so that the tops thereof are evenlyspaced, the cross sectional surfaces of the plurality of the pyramidalprojections 1327, 1627 a, and 1627 b have the same shape as shown inFIGS. 10 and 11. The plurality of the pyramidal projections 1327, 1627a, and 1627 b are arranged so as to be in contact with each other andeach side of the base of the pyramidal projection is in contact with oneside of the base of the adjacent pyramidal projection. Therefore, inthis embodiment mode, the plurality of pyramidal projections arearranged with no space therebetween and cover the display screen surfaceas shown in FIGS. 10 and 11. A plane portion of the display screensurface is not exposed by the plurality of pyramidal projections andincident light from external is incident on sloped surfaces of theplurality of pyramidal projections, so that reflection of incident lightfrom external on the plane portion can be reduced.

In this embodiment mode, the distance between the tops of the pluralityof pyramidal projections and the width of the base of the pyramidalprojection are preferably equal to or shorter than 350 nm, and theheight of each of the plurality of pyramidal projections is preferablyequal to or longer than 800 nm. The fill rate of bases of the pluralityof pyramidal projections per unit area of the surface of a displayscreen (the rate of the display screen which is filled (occupied)) isequal to or more than 80%, preferably equal to or more than 90%. A fillrate is a rate of a formation region of pyramidal projections over adisplay screen surface. When the fill rate is equal to or more than 80%,the rate of plane portions where no pyramidal projection is formed(which is parallel to the display screen) is equal to or less than 20%.The ratio of the height of a pyramidal projection to the width of a basethereof is equal to or more than 5. Under the above-described condition,the rate of light incident from external on the plane portion is reducedand thus reflection with respect to the viewer side can be prevented.

Further, the plurality of pyramidal projections preferably have manymore sides having angles with respect to the bases thereof becauseincident light from external are scattered in many more directions. Inthis embodiment mode, a pyramidal projection has six sides which are incontact with and at an angle to a base. In addition, since the base of apyramidal projection shares a vertex with bases of other two pyramidalprojections and the pyramidal projection has a plurality of sides whichare provided at an angle, incident light is more easily reflected inmany directions. Therefore, the more vertices the base of a pyramidalprojection has, the more easily an anti-reflection function thereof canbe exerted, and the pyramidal projection has six vertices of the base.The pyramidal projections each having a hexagonal pyramidal base of thisembodiment mode have shapes capable of being densely arranged with nospace therebetween, which are optimal shapes each having the largestnumber of sides of any pyramidal projection and a high anti-reflectionfunction with which incident light can be scattered efficiently in manydirections.

Since the plurality of pyramidal projections 1327, 1627 a, and 1627 b ofthis embodiment mode are arranged so that the tops thereof are evenlyspaced, isosceles triangles having the same shapes are adjacent to eachother in cross section.

The display device of this embodiment mode has a plurality of pyramidalprojections on the surface thereof. Reflected incident light fromexternal is reflected to not the viewer side but another adjacentpyramidal projection because a side surface of each pyramidal projectionis not horizontal. Alternatively, reflected incident light propagatesbetween adjacent pyramidal projections. Incident light from external ispartly transmitted through a pyramidal projection, and the rest of theincident light from external, which is reflected light, is then incidenton an adjacent pyramidal projection. In this manner, the incident lightfrom external which is reflected by a side surface of the pyramidalprojection repeats incidence on adjacent pyramidal projections.

That is, the number of times that incident light from external isincident on the pyramidal projections, of the incident light fromexternal which is incident on the display device, is increased;therefore, the amount of light transmitted through the pyramidalprojections is increased. Thus, the amount of light from externalreflected to the viewer side is reduced, and the cause of a reduction invisibility such as reflection can be prevented.

This embodiment mode can provide a high-visibility display device havingan anti-reflection function with which reflection of incident light fromexternal can be further reduced by being provided with a plurality ofpyramidal projections on their surface. Accordingly, a more high-qualityand high-performance display device can be manufactured.

This embodiment mode can be freely combined with Embodiment Mode 1

Embodiment Mode 7

In this embodiment mode, an example of a display device having ananti-reflection function with which reflection of incident light fromexternal can be further reduced, for the purpose of providing excellentvisibility, is described. Specifically, a light-emitting display deviceusing a light-emitting element as a display element is described.

In this embodiment mode, a structure of a light-emitting elementapplicable to a display element of the display device of the presentinvention is described with reference to FIGS. 22A to 22D.

FIGS. 22A to 22D each show an element structure of a light-emittingelement. In the light-emitting element, an electroluminescent layer 860in which an organic compound and an inorganic compound are mixed isinterposed between a first electrode layer 870 and a second electrodelayer 850. The electroluminescent layer 860 includes a first layer 804,a second layer 803, and a third layer 802 as shown, and in particular,the first layer 804 and the third layer 802 are highly characteristic.

First, the first layer 804 is a layer which has a function oftransporting holes to the second layer 803, and includes at least afirst organic compound and a first inorganic compound showing anelectron-accepting property with respect to the first organic compound.It is important that the first organic compound and the first inorganiccompound are not simply mixed but the first inorganic compound has anelectron-accepting property with respect to the first organic compound.With this structure, many hole-carriers are generated in the firstorganic compound having originally almost no inherent carriers, and ahole-injecting property and hole-transporting property which areextremely excellent are obtained.

Therefore, as for the first layer 804, not only an advantageous effectthat is considered to be obtained by mixing an organic compound and aninorganic compound (such as improvement in heat resistance) but alsoexcellent conductivity (in particular, a hole-injecting property and ahole-transporting property in the first layer 804) can be obtained. Thisexcellent conductivity is an advantageous effect which cannot beobtained in a conventional hole-transporting layer in which an organiccompound and an inorganic compound that do not electronically interactwith each other are simply mixed. This advantageous effect can make adriving voltage lower than the conventional case. In addition, since thefirst layer 804 can be made thick without causing a rise in drivingvoltage, short circuit of the element due to dusts or the like can besuppressed.

It is preferable to use a hole-transporting organic compound as thefirst organic compound because hole carriers are generated in the firstorganic compound as described above. The hole-transporting organiccompound includes, for example, phthalocyanine (abbreviation: H₂Pc),copper phthalocyanine (abbreviation: CuPc), vanadyl phthalocyanine(abbreviation: VOPc), 4,4′,4″-tris(N,N-diphenylamino)triphenylamine(abbreviation: TDATA),4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine(abbreviation: MTDATA), 1,3,5-tris[N,N-di(m-tolyl)amino]benzene(abbreviation: m-MTDAB),N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine(abbreviation: TPD), 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl(abbreviation: NPB),4,4′-bis{N-[4-di(m-tolyl)amino]phenyl-N-phenylamino}biphenyl(abbreviation: DNTPD), 4,4′,4″-tris(N-carbazolyl)triphenylamine(abbreviation: TCTA), and the like. However, the present invention isnot limited thereto. Among the compounds described above, aromatic aminecompounds typified by TDATA, MTDATA, m-MTDAB, TPD, NPB, DNTPD, and TCTAcan easily generate hole carriers and are suitable compound groups forthe first organic compound.

On the other hand, the first inorganic compound may be any material aslong as the material can easily accept electrons from the first organiccompound, and various kinds of metal oxides and metal nitrides may beused. Oxides of any of transition metals that belong to Groups 4 to 12of the periodic table is preferable because an electron-acceptingproperty is easily provided. Specifically, titanium oxide, zirconiumoxide, vanadium oxide, molybdenum oxide, tungsten oxide, rhenium oxide,ruthenium oxide, zinc oxide, and the like can be given. Among the metaloxides described above, oxides of any of transition metals that belongto Groups 4 to 8 of the periodic table mostly has a highelectron-accepting property and is a preferable group. In particular,vanadium oxide, molybdenum oxide, tungsten oxide, and rhenium oxide arepreferable because they can be treated by vacuum evaporation and can beeasily used.

It is to be noted that the first layer 804 may be formed by stacking ofa plurality of layers each containing a combination of the organiccompound and the inorganic compound described above, or may furthercontain another organic compound or inorganic compound.

Next, the third layer 802 is described. The third layer 802 is a layerhaving a function of transporting electrons to the second layer 803 andincludes at least a third organic compound and a third inorganiccompound showing an electron-donating property to the third organiccompound. It is important that the third organic compound and the thirdinorganic compound are not simply mixed but the third inorganic compoundhas an electron-donating property with respect to the third organiccompound. With this structure, many electron-carriers are generated inthe third organic compound which has originally almost no inherentcarriers, and an electron-injecting and an electron-transportingproperty which are highly excellent can be obtained.

Therefore, as for the third layer 802, not only an advantageous effectthat is considered to be obtained by mixing an organic compound and aninorganic compound (such as improvement in heat resistance) but alsoexcellent conductivity (in particular, a hole-injecting property and ahole-transporting property in the third layer 802) can be obtained. Thisexcellent conductivity is an advantageous effect which cannot beobtained in a conventional hole-transporting layer in which an organiccompound and an inorganic compound that do not electronically interactwith each other are simply mixed. This advantageous effect can make adriving voltage lower than the conventional case. In addition, since thethird layer 802 can be made thick without causing a rise in drivingvoltage, short circuit of the element due to dusts or the like can besuppressed.

It is preferable to use an electron-transporting organic compound as thethird organic compound because electron carriers are generated in thethird organic compound as described above. The electron-transportingorganic compound includes, for example, tris(8-quinolinolato)aluminum(abbreviation: Alq₃), tris(4-methyl-8-quinolinolato)aluminum(abbreviation: Almq₃), bis(10-hydroxybenzo[h]-quinolinato)beryllium(abbreviation: BeBq₂),bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum (abbreviation:BAlq), bis[2-(2′-hydroxyphenyl)benzoxazolato]zinc (abbreviation:Zn(BOX)₂), bis[2-(2′-hydroxyphenyl)benzothiazolato]zinc (abbreviation:Zn(BTZ)₂), bathophenanthroline (abbreviation: BPhen), bathocuproin(abbreviation: BCP),2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 1,3-bis[5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),2,2′,2″-(1,3,5-benzenetriyl)-tris(1-phenyl-1H-benzimidazole)(abbreviation: TPBI),3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole(abbreviation: TAZ),3-(4-biphenylyl)-4-(4-ethylphenyl)-5-(4-tert-butylphenyl)-1,2,4-triazole(abbreviation: p-EtTAZ), and the like. However, the present invention isnot limited thereto. Among the compounds mentioned above, chelate metalcomplexes each having a chelate ligand including an aromatic ringtypified by Alq₃, Almq₃, BeBq₂, BAlq, Zn(BOX)₂, and Zn(BTZ)₂, organiccompounds having a phenanthroline skeleton typified by BPhen and BCP,and organic compounds having an oxadiazole skeleton typified by PBD andOXD-7 can easily generate electron carriers and are suitable compoundgroups for the third organic compound.

On the other hand, the third inorganic compound may be any material aslong as the material can easily donate electrons to the third organiccompound, and various kinds of metal oxide and metal nitride can beused. Alkali metal oxide, alkaline-earth metal oxide, rare-earth metaloxide, alkali metal nitride, alkaline-earth metal nitride, andrare-earth metal nitride are preferable because an electron-donatingproperty is easily provided. Specifically, for example, lithium oxide,strontium oxide, barium oxide, erbium oxide, lithium nitride, magnesiumnitride, calcium nitride, yttrium nitride, lanthanum nitride, and thelike can be given. In particular, lithium oxide, barium oxide, lithiumnitride, magnesium nitride, and calcium nitride are preferable becausethey can be treated by vacuum evaporation and can be easily used.

It is to be noted that the third layer 802 may be formed by stacking ofa plurality of layers each containing a combination of the organiccompound and the inorganic compound described above, or may furthercontain another organic compound or inorganic compound.

Then, the second layer 803 is described. The second layer 803 is a layerhaving a function of emitting light and includes a second organiccompound having a light-emitting property. The second layer 803 mayinclude a second inorganic compound. The second layer 803 may be formedusing various light-emitting organic compounds and inorganic compounds.However, since it is considered that a current does not easily flowsthrough the second layer 803 as compared to through the first layer 804or the third layer 802, the thickness of the second layer 803 ispreferably approximately 10 to 100 nm.

There are no particular limitations on the second organic compound aslong as it is a light-emitting organic compound. The second organiccompound includes, for example, 9,10-di(2-naphthyl)anthracene(abbreviation: DNA), 9,10-di(2-naphthyl)-2-tert-butylanthracene(abbreviation: t-BuDNA), 4,4′-bis(2,2-diphenylvinyl)biphenyl(abbreviation: DPVBi), coumarin 30, coumarin 6, coumarin 545, coumarin545T, perylene, rubrene, periflanthene,2,5,8,11-tetra(tert-butyl)perylene (abbreviation: TBP),9,10-diphenylanthracene (abbreviation: DPA), 5,12-diphenyltetracene,4-(dicyanomethylene)-2-methyl-[p-(dimethylamino)styryl]-4H-pyran(abbreviation: DCM1),4-(dicyanomethylene)-2-methyl-6-[2-(julolidin-9-yl)ethenyl]-4H-pyran(abbreviation: DCM2),4-(dicyanomethylene)-2,6-bis[p-(dimethylamino)styryl]-4H-pyran(abbreviation: BisDCM), and the like. Alternatively, a compound capableof emitting phosphorescence such asbis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(picolinate)(abbreviation: FIrpic),bis{2-[3′,5′-bis(trifluoromethyl)phenyl]pyridinato-N,C^(2′)}iridium(picolinate)(abbreviation: Ir(CF₃ ppy)₂(pic)),tris(2-phenylpyridinato-N,C^(2′))iridium (abbreviation: Ir(ppy)₃),bis(2-phenylpyridinato-N,C^(2′))iridium(acetylacetonate) (abbreviation:Ir(ppy)₂(acac)),bis[2-(2′-thienyl)pyridinato-N,C^(3′)]iridium(acetylacetonate)(abbreviation: Ir(thp)₂(acac)),bis(2-phenylquinolinato-N,C^(2′))iridium(acetylacetonate) (abbreviation:Ir(pq)₂(acac)), or bis[2-(2′-benzothienylpyridinato-N,C^(3′)]iridium(acetylacetonate) (abbreviation:Ir(btp)₂(acac)) may be used.

Further, a triplet excitation light-emitting material containing a metalcomplex or the like may be used for the second layer 803 in addition toa singlet excitation light-emitting material. For example, among pixelsemitting light of red, green, and blue, the pixel emitting light of redwhose luminance is reduced by half in a relatively short time is formedusing a triplet excitation light-emitting material and the other pixelsare formed using a singlet excitation light-emitting material. A tripletexcitation light-emitting material has a feature that light-emittingefficiency is favorable so that less power is consumed to obtain thesame luminance. In other words, when a triplet excitation light-emittingmaterial is used for the pixel emitting light of red, only a smallamount of current is necessarily applied to a light-emitting element;thus, reliability can be improved. The pixel emitting light of red andthe pixel emitting light of green may be formed using a tripletexcitation light-emitting material and the pixel emitting light of bluemay be formed using a singlet excitation light-emitting material inorder to achieve low power consumption. Low power consumption can befurther achieved by formation of a light-emitting element emitting lightof green that has high visibility for a human eye with the use of atriplet excitation light-emitting material.

The second layer 803 may be added with not only the second organiccompound described above, which emits light, but also another organiccompound. An organic compound that can be added includes, for example,TDATA, MTDATA, m-MTDAB, TPD, NPB, DNTPD, TCTA, Alq₃, Almq₃, BeBq₂, BAlq,Zn(BOX)₂, Zn(BTZ)₂, BPhen, BCP, PBD, OXD-7, TPBI, TAZ, p-EtTAZ, DNA,t-BuDNA, and DPVBi, which are mentioned above, and4,4′-bis(N-carbazolyl)biphenyl (abbreviation: CBP),1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB), and thelike. However, the present invention is not limited thereto. It ispreferable that the organic compound which is added in addition to thesecond organic compound have larger excitation energy than the secondorganic compound and be added by larger amount than the second organiccompound, in order to make the second organic compound emit lightefficiently (which makes it possible to prevent concentration quenchingof the second organic compound). Alternatively, as another function, theadded organic compound may emit light along with the second organiccompound (which makes it possible to emit white light or the like).

The second layer 803 may have a structure where color display isperformed by formation of a light-emitting layer having a differentemission wavelength range for each pixel. Typically, a light-emittinglayer corresponding to each of R (red), G (green), and B (blue) isformed. Also in this case, color purity can be improved and a pixelportion can be prevented from having a mirror surface (reflecting) byprovision of a filter which transmits light of the emission wavelengthrange on the light-emission side of the pixel. By provision of thefilter, a circularly polarizing plate or the like that has beenconsidered to be necessary can be omitted, and further, the loss oflight emitted from the light-emitting layer can be eliminated. Further,change in color tone, which occurs when a pixel portion (display screen)is obliquely seen, can be reduced.

Either a low-molecular organic light-emitting material or ahigh-molecular organic light-emitting material may be used for amaterial of the second layer 803. A high-molecular organiclight-emitting material has higher physical strength and higherdurability of the element than a low-molecular material. In addition,since a high-molecular organic light-emitting material can be formed bycoating, the element can be relatively easily formed.

The emission color is determined depending on a material forming thelight-emitting layer; therefore, a light-emitting element which emitsdesired light can be formed by selecting an appropriate material for thelight-emitting layer. As a high-molecular electroluminescent materialwhich can be used for forming a light-emitting layer; apolyparaphenylene-vinylene-based material, a polyparaphenylene-basedmaterial, a polythiophene-based material, a polyfluorene-based material,and the like can be given.

As the polyparaphenylene-vinylene-based material, a derivative ofpoly(paraphenylenevinylene) [PPV] such aspoly(2,5-dialkoxy-1,4-phenylenevinylene) [RO-PPV],poly(2-(2′-ethyl-hexoxy)-5-methoxy-1,4-phenylenevinylene) [MEH-PPV], orpoly(2-(dialkoxyphenyl)-1,4-phenylenevinylene) [ROPh-PPV] can be given.As the polyparaphenylene-based material, a derivative ofpolyparaphenylene [PPP] such as poly(2,5-dialkoxy-1,4-phenylene)[RO-PPP] or poly(2,5-dihexoxy-1,4-phenylene) can be given. As thepolythiophene-based material, a derivative of polythiophene [PT] such aspoly(3-alkylthiophene) [PAT], poly(3-hexylthiophen) [PHT],poly(3-cyclohexylthiophen) [PCHT], poly(3-cyclohexyl-4-methylthiophene)[PCHMT], poly(3,4-dicyclohexylthiophene) [PDCHT],poly[3-(4-octylphenyl)-thiophene] [POPT], orpoly[3-(4-octylphenyl)-2,2bithiophene] [PTOPT] can be given. As thepolyfluorene-based material, a derivative of polyfluorene [PF] such aspoly(9,9-dialkylfluorene) [PDAF] or poly(9,9-dioctylfluorene) [PDOF] canbe given.

The second inorganic compound may be any inorganic compound as long aslight emission of the second organic compound is not easily quenched bythe inorganic compound, and various kinds of metal oxide and metalnitride may be used. In particular, a metal oxide having a metal thatbelongs to Group 13 or 14 of the periodic table is preferable becauselight emission of the second organic compound is not easily quenched,and specifically, aluminum oxide, gallium oxide, silicon oxide, andgermanium oxide are preferable. However, the second inorganic compoundis not limited thereto.

It is to be noted that the second layer 803 may be formed by stacking ofa plurality of layers each containing a combination of the organiccompound and the inorganic compound, which are described above, or mayfurther include another organic compound or inorganic compound. A layerstructure of the light-emitting layer can be changed, and a dedicatedelectrode layer may be provided or a light-emitting material may bedispersed, instead of provision of no specific electron-injecting regionor light-emitting region. Such a change can be permitted unless itdeparts from the spirit of the present invention.

A light-emitting element formed using the above materials emits light bybeing forwardly biased. A pixel of a display device which is formedusing a light-emitting element can be driven by a simple matrix mode oran active matrix mode. In any case, each pixel emits light byapplication of forward bias thereto at a specific timing; however, thepixel is in a non-emitting state for a certain period. Reliability of alight-emitting element can be improved by application of reverse bias inthe non-emitting time, In a light-emitting element, there is adeterioration mode in which emission intensity is decreased under aconstant driving condition or a deterioration mode in which anon-light-emitting region is increased in the pixel and luminance isapparently decreased. However, progression of deterioration can beslowed down by performing of alternating driving where bias is appliedforwardly and reversely; thus, reliability of a light-emitting displaydevice can be improved. In addition, either digital driving or analogdriving can be applied.

A color filter (colored layer) may be formed over a sealing substrate.The color filter (colored layer) can be formed by an evaporation methodor a droplet discharging method. High-definition display can beperformed with the use of the color filter (colored layer). This isbecause a broad peak can be modified to be sharp in an emission spectrumof each of R, G, and B by the color filter (colored layer).

A material emitting light of a single color is formed and it is combinedwith a color filter or a color conversion layer, so that full colordisplay can be performed. The color filter (colored layer) or the colorconversion layer may be formed over, for example, the seating substrateand attached to an element substrate.

It is needless to say that display of a single color emission may beperformed. For example, an area color type display device may be formedusing single color emission. The area color type display device issuitable for a passive matrix display portion and can mainly displaycharacters and symbols.

Materials for the first electrode layer 870 and the second electrodelayer 850 are necessary to be selected considering the work function.The first electrode layer 870 and the second electrode layer 850 can beeither an anode or a cathode depending on the pixel structure. In a casewhere the polarity of a driving thin film transistor is a p-channeltype, the first electrode layer 870 preferably serves as an anode andthe second electrode layer 850 preferably serves as a cathode as shownin FIG. 22A. In the case where the polarity of the driving thin filmtransistor is an n-channel type, the first electrode layer 870preferably serves as a cathode and the second electrode layer 850preferably serves as an anode as shown in FIG. 22B. Materials that canbe used for the first electrode layer 870 and the second electrode layer850 are described below. It is preferable to use a material having ahigh work fuction (specifically, a material having a work function of4.5 eV or more) for one of the first electrode layer 870 and the secondelectrode layer 850, which serves as an anode, and a material having alow work function (specifically, a material having a work function of3.5 eV or less) for the other electrode layer which serves as a cathode.However, since the first layer 804 is superior in a hole-injectingproperty and a hole-transporting property and the third layer 802 issuperior in an electron-injecting property and an electron transportingproperty, both the first electrode layer 870 and the second electrodelayer 850 are scarcely restricted by a work function and variousmaterials can be used.

The light-emitting elements in FIGS. 22A and 22B each have a structurewhere light is extracted from the first electrode layer 870 and thus,the second electrode layer 850 is not necessary to have alight-transmitting property. The second electrode layer 850 may beformed from a film mainly containing an element selected from Ti, Ni, W,Cr, Pt, Zn, Sn, In, Ta, Al, Cu, Au, Ag, Mg, Ca, Li and Mo, or an alloymaterial or a compound material containing the above element as its maincomponent, such as titanium nitride, TiSi_(X)N_(Y), WSi_(X), tungstennitride, WSi_(X)N_(Y), or NbN; or a stacked film thereof with a totalthickness of 100 to 800 nm.

The second electrode layer 850 can be formed by an evaporation method, asputtering method, a CVD method, a printing method, a dispenser method,a droplet discharging method, or the like.

In addition, when the second electrode layer 850 is formed using alight-transmitting conductive material similarly to the material usedfor the first electrode layer 870, light can be extracted from thesecond electrode layer 850 as well, and a dual emission structure can beobtained, in which light emitted from the light-emitting element isemitted from both the first electrode layer 870 and the second electrodelayer 850.

It is to be noted that the light-emitting element of the presentinvention can have variations by changing of types of the firstelectrode layer 870 and the second electrode layer 850.

FIG. 22B shows the case where the electroluminescent layer 860 is formedby stacking of the third layer 802, the second layer 803, and the firstlayer 804 in this order on the first electrode layer 870 side.

As described above, in the light-emitting element of the presentinvention, the layer interposed between the first electrode layer 870and the second electrode layer 850 is formed of the electroluminescentlayer 860 including a layer in which an organic compound and aninorganic compound are combined. The light-emitting element is anorganic-inorganic composite light-emitting element provided with layers(that is, the first layer 804 and the third layer 802) that providefunctions of a high carrier-injecting property and carrier-transportingproperty by mixing of an organic compound and an inorganic compound.Such functions as high carrier-injecting property andcarrier-transporting property cannot be obtained from only either one ofthe organic compound or the inorganic compound. In addition, the firstlayer 804 and the third layer 802 are particularly necessary to belayers in which an organic compound and an inorganic compound arecombined when provided on the first electrode layer 870 side, and maycontain only one of an organic compound and an inorganic compound whenprovided on the second electrode layer 850 side.

Further, known various methods can be used as a method for forming theelectroluminescent layer 860, which is a layer in which an organiccompound and an inorganic compound are mixed. For example, the methodsinclude a co-evaporation method for vaporizing both an organic compoundand an inorganic compound by resistance heating. Alternatively, forco-evaporation, an inorganic compound may be vaporized by an electronbeam (EB) while an organic compound is vaporized by resistance heating.Further alternatively, a method for sputtering an inorganic compoundwhile vaporizing an organic compound by resistance heating to depositthe both at the same time. Instead, the electroluminescent layer 860 maybe formed by a wet method.

In the same manner, for the first electrode layer 870 and the secondelectrode layer 850, an evaporation method by resistance heating, an EBevaporation method, a sputtering method, a wet method, or the like canbe used.

In FIG. 22C, an electrode layer having reflectivity is used for thefirst electrode layer 870, and an electrode layer having alight-transmitting property is used for the second electrode layer 850in the structure of FIG. 22A. Light emitted from the light-emittingelement is reflected off the first electrode layer 870, transmittedthrough the second electrode layer 850, and is emitted. Similarly, inFIG. 22D, an electrode layer having reflectivity is used for the firstelectrode layer 870, and an electrode layer having a light-transmittingproperty is used for the second electrode layer 850 in the structure ofFIG. 22B. Light emitted from the light-emitting element is reflected offthe first electrode layer 870, transmitted through the second electrodelayer 850, and is emitted.

This embodiment mode can be freely combined with any of the aboveembodiment modes concerning the display device having a light-emittingelement.

In the case of the display device of this embodiment mode, the pluralityof pyramidal projections are densely arranged on a display screensurface. The number of times that incident light from external isincident on the pyramidal projections, of the incident light fromexternal which is incident on the display device, is increased;therefore, the amount of light transmitted through the pyramidalprojections is increased. Thus, the amount of light from externalreflected to the viewer side is reduced, and the cause of a reduction invisibility such as reflection can be prevented.

This embodiment mode can provide a high-visibility display device havingan anti-reflection function with which reflection of incident light fromexternal can be further reduced by being provided with a plurality ofpyramidal projections on their surface. Accordingly, a more high-qualityand high-performance display device can be manufactured.

This embodiment mode can be combined with any of Embodiment Modes 1 to3, 5, and 6 as appropriate.

Embodiment Mode 8

In this embodiment mode, an example of a display device having ananti-reflection function with which reflection of incident light fromexternal can be further reduced, for the purpose of providing excellentvisibility, is described. Specifically, a light-emitting display deviceusing a light-emitting element as a display element is described. Inthis embodiment mode, a structure of a light-emitting element applicableto a display element of the display device of the present invention isdescribed with reference to FIGS. 23A to 24C.

A light-emitting element utilizing electroluminescence is distinguisheddepending on whether a tight-emitting material is an organic compound oran inorganic compound. In general, the former is called an organic ELelement, and the latter is called an inorganic EL element.

The inorganic EL element is categorized into a dispersion inorganic ELelement and a thin-film inorganic EL element depending on its elementstructure. The former and the latter are different in that the formerhas an electroluminescent layer where particles of a light-emittingmaterial are dispersed in a binder, and the latter has anelectroluminescent layer formed of a thin film of a light-emittingmaterial. However, the former and the latter are the same in thatelectrons accelerated by a high electric field are necessary. It is tobe noted that, as a mechanism of light emission that is obtained, thereare donor-acceptor recombination light emission that utilizes a donorlevel and an acceptor level, and localized light emission that utilizesinner-shell electron transition of a metal ion. In many cases, it isgeneral that a dispersion inorganic EL element has donor-acceptorrecombination light emission and a thin-film inorganic EL element haslocalized light emission.

The light-emitting material that can be used in the present inventionincludes a base material and an impurity element to be a light-emissioncenter. An impurity element that is contained is changed, so that lightemission of various colors can be obtained. As a method for forming thelight-emitting material, various methods such as a solid phase methodand a liquid phase method (coprecipitation method) may be used.Alternatively, a spray pyrolysis method, a double decomposition method,a method by heat decomposition reaction of a precursor, a reversedmicelle method, a method in which such a method is combined withhigh-temperature baking, a liquid phase method such as a lyophilizationmethod, or the like may be used.

A solid phase method is a method in which a base material, and animpurity element or a compound containing an impurity element areweighed, mixed in a mortar, heated in an electric furnace, and baked tobe reacted, so that the impurity element is contained in the basematerial. The baking temperature is preferably 700 to 1500° C. This isbecause the solid reaction does not progress when the temperature is toolow, whereas the base material is decomposed when the temperature is toohigh. The baking may be performed in a powder state; however, it ispreferable to perform the baking in a pellet state. Although the bakingis necessary to be performed at relatively high temperature, the solidphase method is easy; therefore, high productivity can be achieved.Thus, the solid phase method is suitable for mass production.

A liquid phase method (coprecipitation method) is a method in which abase material or a compound containing a base material is reacted withan impurity element or a compound containing an impurity element in asolution, dried, and then baked. Particles of a light-emitting materialare distributed uniformly, and the reaction can progress even when thegrain size is small and the baking temperature is low.

As a base material used for a light-emitting material, sulfide, oxide,or nitride can be used. As sulfide, zinc sulfide (ZnS), cadmium sulfide(CdS), calcium sulfide (CaS), yttrium sulfide (Y₂S₃), gallium sulfide(Ga₂S₃), strontium sulfide (SrS), barium sulfide (BaS), or the like canbe used. As oxide, zinc oxide (ZnO), yttrium oxide (Y₂O₃), or the likecan be used. As nitride, aluminum nitride (AlN), gallium nitride (GaN),indium nitride (InN), or the like can be used. Alternatively, zincselenide (ZnSe), zinc telluride (ZnTe), or the like may be used, or aternary mixed crystal such as calcium-gallium sulfide (CaGa₂S₄),strontium-gallium sulfide (SrGa₂S₄), or barium-gallium sulfide (BaGa₂S₄)may be used.

As a light-emission center of localized light emission, manganese (Mn),copper (Cu), samarium (Sm), terbium (Tb), erbium (Er), thulium (Tm),europium (Eu), cerium (Ce), praseodymium (Pr), or the like can be used.It is to be noted that a halogen element such as fluorine (F) orchlorine (Cl) may be added. A halogen element may have a function ofcompensating a charge.

On the other hand, as a light-emission center of donor-acceptorrecombination light emission, a light-emitting material containing afirst impurity element which forms a donor level and a second impurityelement which forms an acceptor level can be used. As the first impurityelement, fluorine (F), chlorine (Cl), aluminum (Al), or the like can beused. As the second impurity element, copper (Cu), silver (Ag), or thelike can be used.

In the case where the light-emitting material of donor-acceptorrecombination light emission is synthesized by a solid phase method, abase material, the first impurity element or a compound containing afirst impurity element, and the second impurity element or a compoundcontaining the second impurity element are weighed in each, mixed in amortar, heated in an electric furnace, and baked. As the base material,any of the above described base materials can be used. As the firstimpurity element or the compound containing the first impurity element,fluorine (F), chlorine (Cl), aluminum sulfide (Al₂S₃), or the like canbe used. As the second impurity element or the compound containing thesecond impurity element, copper (Cu), silver (Ag), copper sulfide(Cu₂S), silver sulfide (Ag₂S), or the like can be used. The bakingtemperature is preferably 700 to 1500° C. This is because the solidreaction does not progress when the temperature is too low, whereas thebase material is decomposed when the temperature is too high. The bakingmay be performed in a powder state; however, it is preferable to performthe baking in a pellet state.

As the impurity element in the case of utilizing solid reaction, thecompounds containing the first impurity element and the second impurityelement may be combined. In this case, since the impurity element iseasily diffused and solid reaction progresses easily, a uniformlight-emitting material can be obtained. Further, since an unnecessaryimpurity element is not mixed therein, a light-emitting material havinghigh purity can be obtained. As the compounds containing the firstimpurity element and the second impurity element, copper chloride(CuCl), silver chloride (AgCl), or the like can be used.

It is to be noted that the concentration of these impurity elements maybe 0.01 to 10 atomic % with respect to the base material and ispreferably 0.05 to 5 atomic %.

In the case of a thin-film inorganic EL element, an electroluminescentlayer is a layer containing the above light-emitting material, which canbe formed by a vacuum evaporation method such as a resistance heatingevaporation method or an electron beam evaporation (EB evaporation)method, a physical vapor deposition (PVD) method such as a sputteringmethod, a chemical vapor deposition (CVD) method such as a metal organicCVD method or a low-pressure hydride transport CVD method, an atomiclayer epitaxy (ALE) method, or the like.

FIGS. 23A to 23C each show an example of a thin-film inorganic ELelement that can be used as a light-emitting element. In FIGS. 23A to23C, each light-emitting element includes a first electrode layer 50, anelectroluminescent layer 52, and a second electrode layer 53.

The light-emitting elements shown in FIGS. 23B and 23C each have astructure where an insulating layer is provided between the electrodelayer and the electroluminescent layer of the light-emitting element ofFIG. 23A. The light-emitting element shown in FIG. 23B has an insulatinglayer 54 between the first electrode layer 50 and the electroluminescentlayer 52. The light-emitting element shown in FIG. 23C includes aninsulating layer 54 a between the first electrode layer 50 and theelectroluminescent layer 52, and an insulating layer 54 b between thesecond electrode layer 53 and the electroluminescent layer 52. Thus, theinsulating layer may be provided between the electroluminescent layerand one of the electrode layers that sandwich the electroluminescentlayer, or the insulating layer may be provided between theelectroluminescent layer and the first electrode layer and between theelectroluminescent layer and the second electrode layer. Further, theinsulating layer may have a single-layer structure or a stacked-layerstructure including a plurality of layers.

In addition, although the insulating layer 54 is provided so as to be incontact with the first electrode layer 50 in FIG. 23B, the insulatinglayer 54 may be provided so as to be in contact with the secondelectrode layer 53 by reversing of the positions of the insulating layerand the electroluminescent layer.

In the case of a dispersion inorganic EL element, a film-shapedelectroluminescent layer where particles of a light-emitting materialare dispersed in a binder is formed. When particles with desired grainsizes cannot be obtained by a manufacturing method of a light-emittingmaterial, a light-emitting material may be processed into a particlestate by being crushed in a mortar or the like. The binder is asubstance for fixing particles of a light-emitting material in adispersed state to keep the shape of an electroluminescent layer. Thelight-emitting material is uniformly dispersed and fixed in theelectroluminescent layer by the binder.

In the case of a dispersion inorganic EL element, as a formation methodof an electroluminescent layer, a droplet discharging method which canselectively form an electroluminescent layer, a printing method (such asscreen printing or offset printing), a coating method such as a spincoating method, a dipping method, a dispenser method, or the like can beused. There are no particular limitations on the thickness of theelectroluminescent layer; however, a thickness of 10 to 1000 nm ispreferable. In addition, in the electroluminescent layer containing alight-emitting material and a binder, the ratio of the light-emittingmaterial is preferably 50 to 80 wt %.

FIGS. 24A to 24C each show an example of a dispersion inorganic ELelement that can be used as a light-emitting element. In FIG. 24A, thelight-emitting element has a stacked-layer structure of a firstelectrode layer 60, an electroluminescent layer 62, and a secondelectrode layer 63, in which a light-emitting material 61 held by abinder is contained in the electroluminescent layer 62.

As the binder that can be used in this embodiment mode, an organicmaterial or an inorganic material can be used, or a mixed material of anorganic material and an inorganic material may be used. As the organicmaterial, a polymer having a relatively high dielectric constant like acyanoethyl cellulose-based resin, or a resin such as polyethylene,polypropylene, a polystyrene-based resin, a silicone resin, an epoxyresin, or vinylidene fluoride can be used. Alternatively, aheat-resistant high molecular such as aromatic polyamide orpolybenzimidazole, or a siloxane resin may be used. A siloxane resincorresponds to a resin containing a Si—O—Si bond. Siloxane is composedof a skeleton structure formed by the bond of silicon (Si) and oxygen(O). As a substituent thereof, an organic group containing at leasthydrogen (such as an alkyl group or aromatic hydrocarbon) is used.Instead, a fluoro group, or a fluoro group and an organic groupcontaining at least hydrogen may be used as the substituent. Furtheralternatively, a resin material such as a vinyl resin, for example,polyvinyl alcohol or polyvinyl butyral, a phenol resin, a novolac resin,an acrylic resin, a melamine resin, a urethane resin, or an oxazoleresin (polybenzoxazole) may be used. A dielectric constant can becontrolled by mixing of these resins with high-dielectric constantmicroparticles of barium titanate (BaTiO₃), strontium titanate (SrTiO₃),or the like as appropriate.

As the inorganic material contained in the binder, a material selectedfrom silicon oxide (SiO_(x)), silicon nitride (SiN_(x)), siliconcontaining oxygen and nitrogen, aluminum nitride (AlN), aluminumcontaining oxygen and nitrogen, aluminum oxide (Al₂O₃), titanium oxide(TiO₂), BaTiO₃, SrTiO₃, lead titanate (PbTiO₃), potassium niobate(KNbO₃), lead niobate (PbNbO₃), tantalum oxide (Ta₂O₅), barium tantalate(BaTa₂O₆), lithium tantalate (LiTaO₃), yttrium oxide (Y₂O₃), zirconiumoxide (ZrO₂), and other substances containing an inorganic insulatingmaterial can be used. By mixing of the organic material with ahigh-dielectric constant inorganic material (by addition or the like), adielectric constant of an electroluminescent layer containing alight-emitting material and a binder can be controlled much better andfurther increased. When a mixed layer of an inorganic material and anorganic material is used for the binder to have a high dielectricconstant, a larger electric charge can be induced by the light-emittingmaterial.

In a manufacturing process, the light-emitting material is dispersed ina solution containing a binder. As a solvent of the solution containinga binder that can be used in this embodiment mode, it is preferable toselect a solvent that dissolves a binder material and can make asolution with the viscosity appropriate for a method for forming theelectroluminescent layer (various wet processes) and for a desired filmthickness. An organic solvent or the like can be used, and for example,when a siloxane resin is used as the binder, propylene glycolmonomethylether, propylene glycolmonomethyl ether acetate (also referred to asPGMEA), 3-methoxy-3-methyl-1-butanol (also referred to as MMB), or thelike can be used.

The light-emitting elements shown in FIGS. 24B and 24C each have astructure where an insulating layer is provided between the electrodelayer and the electroluminescent layer of the light-emitting element ofFIG. 24A. The light-emitting element shown in FIG. 24B has an insulatinglayer 64 between the first electrode layer 60 and the electroluminescentlayer 62. The light-emitting element shown in FIG. 24C includes aninsulating layer 64 a between the first electrode layer 60 and theelectroluminescent layer 62, and an insulating layer 64 b between thesecond electrode layer 63 and the electroluminescent layer 62. Thus, theinsulating layer may be provided between the electroluminescent layerand one of the electrode layers that sandwich the electroluminescentlayer, or the insulating layers may be provided between theelectroluminescent layer and the first electrode layer and between theelectroluminescent layer and the second electrode layer. Further, theinsulating layer may have a single-layer structure or a stacked-layerstructure including a plurality of layers.

In addition, although the insulating layer 64 is provided so as to be incontact with the first electrode layer 60 in FIG. 24B, the insulatinglayer 64 may be provided so as to be in contact with the secondelectrode layer 63 by reversing of the positions of the insulating layerand the electroluminescent layer.

Although the insulating layers 54 and 64 in FIGS. 23B, 23C, 24B and 24Care not particularly limited, such insulating layers preferably have ahigh withstand voltage and dense film qualities, and more preferablyhave a high dielectric constant. For example, silicon oxide (SiO₂),yttrium oxide (Y₂O₃), titanium oxide (TiO₂), aluminum oxide (Al₂O₃),hafnium oxide (HfO₂), tantalum oxide (Ta₂O₅), barium titanate (BaTiO₃),strontium titanate (SrTiO₃), lead titanate (PbTiO₃), silicon nitride(Si₃N₄), zirconium oxide (ZrO₂), or the like, or a mixed film or astaked-layer film of two or more kinds thereof can be used. Theseinsulating films can be formed by sputtering, evaporation, CVD, or thelike. Alternatively, the insulating layers may be formed by dispersingof particles of these insulating materials in a binder. The bindermaterial may be formed of the same material and by the same method asthe binder contained in the electroluminescent layer. A thickness of theinsulating layer is not particularly limited, and a thickness of 10 to1000 nm is preferable.

The light-emitting element described in this embodiment mode can emitlight by application of a voltage between the pair of electrodes whichsandwich the electroluminescent layer, and can be operated by directcurrent driving or alternating current driving.

In the case of the display device of this embodiment mode, the pluralityof pyramidal projections are densely arranged on a display screensurface. The number of times that incident light from external isincident on the pyramidal projections, of the incident light fromexternal which is incident on the display device, is increased;therefore, the amount of light transmitted through the pyramidalprojections is increased. Thus, the amount of light from externalreflected to the viewer side is reduced, and the cause of a reduction invisibility such as reflection can be prevented.

This embodiment mode can provide a high-visibility display device havingan anti-reflection function with which reflection of incident light fromexternal can be further reduced by being provided with a plurality ofpyramidal projections on their surface. Accordingly, a more high-qualityand high-performance display device can be manufactured.

This embodiment mode can be combined with any of Embodiment Modes 1 to3, 5, and 6 as appropriate.

Embodiment Mode 9

In this embodiment mode, a structure of a backlight is described. Abacklight is provided in a display device as a backlight unit having alight source, and the light source of the backlight unit is surroundedby a reflection plate for scattering light efficiently.

As shown in FIG. 16A, a cold cathode fluorescent lamp 401 can be used asa light source of a backlight unit 352. In addition, a lamp reflector332 can be provided to reflect light from the cold cathode fluorescentlamp 401 efficiently. The cold cathode fluorescent lamp 401 is oftenused for a large display device for intensity of luminance from the coldcathode fluorescent lamp. Therefore, such a backlight unit having a coldcathode fluorescent lamp can be used for a display of a personalcomputer.

As shown in FIG. 16B, light-emitting diodes (LED) 402 can be used aslight sources of the backlight unit 352. For example, light-emittingdiodes (W) 402 which emit white light are provided at predeterminedintervals. In addition, the lamp reflector 332 can be provided toreflect light from the light-emitting diode (W) 402 efficiently.

As shown in FIG. 16C, light-emitting diodes (LED) 403, 404, and 405 ofRGB colors can be used as light sources of the backlight unit 352. Byusing the light-emitting diodes (LED) 403, 404, and 405 of RGB colors,higher color reproducibility can be realized in comparison with the casewhere only the light-emitting diode (W) 402 which emits white light isused. In addition, the lamp reflector 332 can be provided to reflectlight from the light-emitting diodes efficiently.

Further, as shown in FIG. 16D, in the case where the light-emittingdiodes (LED) 403, 404, and 405 of RGB colors are used as light sources,the number and arrangement thereof are not necessarily the same. Forexample, a plurality of light-emitting diodes of a color having lowemission intensity (for example, green) may be arranged.

Further, the light-emitting diode 402 which emits white light may beused in combination with the light-emitting diodes (LED) 403, 404, and405 of RGB colors.

Note that in the case of having the light-emitting diodes of RGB colors,the light-emitting diodes sequentially emit light in accordance withtime by applying a field sequential mode, so that color display can beperformed.

Using a light-emitting diode is suitable for a large display devicesince luminance is high. Further, purity of ROB colors is high;therefore, a light-emitting diode has excellent color reproducibility ascompared to a cold cathode fluorescent lamp. In addition, an arearequired for arrangement can be reduced; therefore, a narrower frame canbe achieved when a light-emitting diode is applied to a small displaydevice.

Further, a light source is not necessarily provided as the backlightunit shown in FIGS. 16A to 16D. For example, in the case where abacklight having a light-emitting diode is mounted on a large displaydevice, the light-emitting diode can be arranged on a back side of thesubstrate. In this case, the light-emitting diodes of ROB colors can besequentially arranged at predetermined intervals. Depending onarrangement of the light-emitting diodes, color reproducibility can beenhanced.

By densely arranging a plurality of pyramidal projections on a surfaceof a display device using such a backlight, a high-visibility displaydevice having a high anti-reflection function with which reflection ofincident light from external can be further reduced can be provided.Therefore, according to the present invention, a high-quality andhigh-performance display device can be manufactured. A backlight havinga light-emitting diode is particularly suitable for a large displaydevice, and a high-quality image can be produced even in a dark place byenhancing the contrast ratio of the large display device.

This embodiment mode can be combined with any of Embodiment Modes 1 to 4as appropriate.

Embodiment Mode 10

FIG. 15 shows an example in which an EL display module manufactured bythe present invention is formed. In FIG. 15, a pixel portion includingpixels is formed over a substrate 2800. As the substrate 2800 and asealing substrate 2820, flexible substrates are used.

In FIG. 15, outside the pixel portion, a TFT similar to that formed in apixel or a protective circuit portion 2801 operated similarly to a diodeby connection of a gate of the TFT and a source or a drain of the TFT isprovided between a driver circuit and the pixel. A driver IC formedusing a single crystalline semiconductor, a stick driver IC formed usinga polycrystalline semiconductor film over a glass substrate, a drivercircuit formed using an SAS, or the like is applied to a driver circuit2809.

The substrate 2800 to which an element layer is transferred is attachedfirmly to a sealing substrate 2820 with spacers 2806 a and 2806 b formedby a droplet discharging method interposed therebetween. The spacers arepreferably provided to keep the distance between two substrates constanteven when the substrate is thin or an area of the pixel portion isincreased. A space between the substrate 2800 and the sealing substrate2820 over light-emitting elements 2804 and 2805 connected to TFTs 2802and 2803, respectively, may be filled with a resin material having alight-transmitting property, and the resin material may be solidified.Alternatively, the space may be filled with anhydrous nitrogen or aninert gas. A plurality of pyramidal projections 2827 are provided on anouter side of the sealing substrate 2820, which is the viewer side.

FIG. 15 shows the case where the light-emitting elements 2804 and 2805are top-emission type and emit light in the direction of arrows shown inthe drawing. Multicolor display can be performed by making each pixelemit light of a different color of red, green, or blue. At this time,color purity of light emitted to an external portion can be improved byformation of colored layers 2807 a, 2807 b, and 2807 c corresponding torespective colors on the sealing substrate 2820 side. Alternatively,pixels as white light-emitting elements may be combined with the coloredlayers 2807 a, 2807 b, and 2807 c.

The driver circuit 2809 which is an external circuit is connected to ascan line or signal line connection terminal, which is provided at oneend of an external circuit board 2811, through a wiring board 2810. Inaddition, a heat pipe 2813 which is a highly efficient thermalconductive device with a pipe shape and a heat sink 2812, which are usedfor radiating heat to the external portion of the device, may beprovided in contact with or adjacent to the substrate 2800 to increase aheat radiation effect.

It is to be noted that FIG. 15 shows the top-emission EL module;however, a bottom-emission structure may be employed by changing of thestructure of the light-emitting element or the position of the externalcircuit board. It is needless to say that a dual-emission structure inwhich light is emitted from both of a top surface and a bottom surfacemay be used. In the case of the top-emission structure, an insulatinglayer serving as a partition may be colored and used as a black matrix.This partition can be formed by a droplet discharging method, and it maybe formed by mixing of a black resin of a pigment material, carbonblack, or the like into a resin material such as polyimide. Instead, astacked layer thereof may be used.

In addition, in an EL display module, reflected incident light fromexternal may be blocked with the use of a retardation plate or apolarizing plate. An insulating layer serving as a partition may becolored to be used as a black matrix. This partition can be formed by adroplet discharging method or the like. Carbon black or the like may bemixed into a black resin of a pigment material or a resin material suchas polyimide to be used, and instead, a stacked layer thereof may beused. By a droplet discharging method, different materials may bedischarged to the same region plural times to form the partition. Aquarter wave plate or a half wave plate may be used as the retardationplate and may be designed to be able to control light. As the structure,the light-emitting element, the sealing substrate (sealing material),the retardation plates (a quarter wave plate (λ/4) and a half wave plate(λ/2)), and the polarizing plate are sequentially formed over a TFTsubstrate, and light emitted from the light-emitting element istransmitted therethrough and is emitted to an external portion from thepolarizing plate side. The retardation plate or polarizing plate may beprovided on a side to which light is emitted or may be provided on bothsides in the case of a dual-emission display device in which light isemitted from the both sides. In addition, a plurality of pyramidalprojections may be provided on the outer side of the polarizing plate.Accordingly, higher-definition and precise images can be displayed.

Although the plurality of pyramidal projections are densely arrangedover the substrate on the viewer side, a sealing structure may be formedby attaching a resin film to the side where the pixel portion is formed,with the use of a sealing material or an adhesive resin, as for asealing structure on a side opposite to the viewer side with an elementinterposed therebetween. Various sealing methods such as resin sealingusing a resin, plastic sealing using plastics, and film sealing using afilm may be employed. A gas barrier film which prevents water vapor frompenetrating the resin film is preferably provided on the surface of theresin film. By employing a film sealing structure, further reduction inthickness and weight can be achieved.

In the case of the display device of this embodiment mode, the pluralityof pyramidal projections are densely arranged on a display screensurface. The number of times that incident light from external isincident on the pyramidal projections, of the incident light fromexternal which is incident on the display device, is increased;therefore, the amount of light transmitted through the pyramidalprojections is increased. Thus, the amount of light from external whichis reflected to the viewer side is reduced, and the cause of a reductionin visibility such as reflection can be prevented.

This embodiment mode can provide a high-visibility display device havingan anti-reflection function with which reflection of incident light fromexternal can be further reduced by being provided with a plurality ofpyramidal projections on their surface. Accordingly, a more high-qualityand high-performance display device can be manufactured.

This embodiment mode can be combined with any of Embodiment Modes 1 to3, 5, and 8 as appropriate.

Embodiment Mode 11

This embodiment mode is described with reference to FIGS. 14A and 14B.FIGS. 14A and 14B show an example in which a display device (liquidcrystal display module) is formed using a TFT substrate 2600manufactured according to the present invention.

FIG. 14A is an example of a liquid crystal display module. The TFTsubstrate 2600 and a counter substrate 2601 are firmly attached to eachother with a sealing material 2602, and a pixel portion 2603 includingTFTs or the like, a display element a liquid crystal layer 2604including a liquid crystal layer, a colored layer 2605, and a polarizingplate 2606 are provided therebetween, thereby forming a display region.The colored layer 2605 is necessary for performing color display, andcolored layers corresponding to red, green, and blue are provided foreach pixel in the case of an RGB mode. The polarizing plate 2606 andpyramidal projections 2626 are provided on an outer side of the countersubstrate 2601, and a polarizing plate 2607 and a diffusing plate 2613are provided on an outer side of the TFT substrate 2600. A light sourceincludes a cold cathode fluorescent lamp 2610 and a reflective plate2611, and a circuit substrate 2612 is connected to the TFT substrate2600 through a flexible wiring board 2609 and includes an externalcircuit such as a control circuit or a power source circuit. Inaddition, a retardation plate may be provided between the polarizingplate and the liquid crystal layer.

The display device of FIG. 14A is an example in which the pyramidalprojections 2626 are provided on an outer side of the counter substrate2601, and the polarizing plate 2606 and the colored layer 2605 aresequentially provided on an inner side. However, the polarizing plate2606 may be provided on the outer side of the counter substrate 2601 (onthe viewer side), and in that case, the pyramidal projections 2626 maybe provided on a surface of the polarizing plate 2606. The stacked-layerstructure of the polarizing plate 2606 and the colored layer 2605 isalso not limited to that of FIG. 14A and may be appropriately determineddepending on materials of the polarizing plate 2606 and the coloredlayer 2605 or conditions of a manufacturing process.

For the liquid crystal display module, a TN (twisted nematic) mode, anIPS (In-Plane-Switching) mode, an FFS (fringe field switching) mode, anMVA (multi-domain vertical alignment) mode, a PVA (patterned verticalalignment) mode, an ASM (axially symmetric aligned micro-cell) mode, anOCB (optical compensated birefringence) mode, an FLC (ferroelectricliquid crystal) mode, an AFLC (antiferroelectric liquid crystal) mode,or the like can be used.

FIG. 14B shows an example of an FS-LCD (field sequential-LCD) in whichan OCB mode is applied to the liquid crystal display module of FIG. 14A.The FS-LCD emits light of red, green, and blue during one frame periodand can perform color display by combining images using time division.Light of each color is emitted by a light-emitting diode, a cold cathodefluorescent lamp, or the like; therefore, a color filter is notnecessary. Thus, it is not necessary to arrange color filters of threeprimary colors and restrict the display region of each color, anddisplay of all three colors can be performed in any region. On the otherhand, since light of three colors is emitted during one frame period,high-speed response is necessary for a liquid crystal. An FLC mode, anOCB mode, or the like each using an FS method is employed for a displaydevice of the present invention, so that a display device or a liquidcrystal television set with high performance and high image quality canbe completed.

A liquid crystal layer of an OCB mode has a so-called π-cell structure,In the π-cell structure, liquid crystal molecules are aligned so thattheir pretilt angles are plane-symmetric with respect to the centerplane between an active matrix substrate and a counter substrate. Anorientation state in a π-cell structure is splay orientation when avoltage is not applied between the substrates, and then shifts to bendorientation when a voltage is applied therebetween. In this bendorientation state, white display is obtained. When a voltage is appliedfurther, liquid crystal molecules of bend orientation get orientatedperpendicular to the both substrates so that light is not transmitted.With the OCB mode, response which is 10 times as rapid as that of aconventional TN mode can be achieved.

Moreover, as a mode for the FS method, an HV (Half-V)-FLC or an SS(surface stabilized)-FLC using ferroelectric liquid crystal (FLC)capable of high-speed operation, or the like may be used. The OCB modecan use nematic liquid crystal having relatively low viscosity, and theHV-FLC or the SS-FLC can use a smectic liquid crystal having aferroelectric phase.

Moreover, optical response speed of a liquid crystal display module getshigher by narrowing of the cell gap of the liquid crystal displaymodule. In addition, the optical response speed can also get higher bydecrease in viscosity of the liquid crystal material. The increase inresponse speed is particularly effective when a pixel pitch in a pixelregion of a TN mode liquid crystal display module is 30 μm or less.Also, further increase in response speed is possible by an overdrivemethod in which an applied voltage is increased (or decreased) for amoment.

FIG. 14B shows a transmissive liquid crystal display module, in which ared light source 2910 a, a green light source 2910 b, and a blue lightsource 2910 c are provided as light sources. The light sources areprovided with a control portion 2912 in order to switch on or off of thered light source 2910 a, the green light source 2910 b, and the bluelight source 2910 c. The control portion 2912 controls light emission ofeach color, light enters the liquid crystal, and images are combinedusing time division, so that color display is performed.

In the case of the display device of this embodiment mode, the pluralityof pyramidal projections are densely arranged on a display screensurface. The number of times that incident light from external isincident on the pyramidal projections, of the incident light fromexternal which is incident on the display device, is increased;therefore, the amount of light transmitted through the pyramidalprojections is increased. Thus, the amount of light from externalreflected to the viewer side is reduced, and the cause of a reduction invisibility such as reflection can be prevented.

This embodiment mode can provide a high-visibility display device havingan anti-reflection function with which reflection of incident light fromexternal can be further reduced by being provided with a plurality ofpyramidal projections on their surface. Accordingly, a more high-qualityand high-performance display device can be manufactured.

This embodiment mode can be combined with any of Embodiment Modes 1 to4, and 9.

Embodiment Mode 12

A television set (also referred to as a TV simply or a televisionreceiver) can be completed using a display device formed by the presentinvention. FIG. 19 is a block diagram showing a main structure of atelevision set.

FIG. 17A is a top plan view showing a structure of a display panel ofthe present invention, in which a pixel portion 2701 where pixels 2702are arranged in matrix, a scan line input terminal 2703, and a signalline input terminal 2704 are formed over a substrate 2700 having aninsulating surface. The number of pixels may be set in accordance withvarious standards: the number of pixels of XGA for RGB full-colordisplay may be 1024×768×3 (RGB), that of UXGA for RGB full-color displaymay be 1600×1200×3 (RGB), and that corresponding to a full-speck highvision for RGB full-color display may be 1920×1080×3 (ROB).

Scan lines which extend from the scan line input terminal 2703intersects with signal lines which extend from the signal line inputterminal 2704, so that the pixels 2702 are arranged in matrix. Eachpixel in the pixel portion 2701 is provided with a switching element anda pixel electrode layer connected to the switching element. A typicalexample of the switching element is a TFT. A gate electrode layer sideof the TFT is connected to the scan line, and a source or drain sidethereof is connected to the signal line, so that each pixel can becontrolled independently by a signal inputted externally.

FIG. 17A shows a structure of the display panel in which signalsinputted to a scan line and a signal line are controlled by an externaldriver circuit. Alternatively, driver ICs 2751 may be mounted on thesubstrate 2700 by a COG (chip on glass) method as shown in FIG. 18A.Alternatively, a TAB (tape automated bonding) method may be employed asshown in FIG. 181B. The driver ICs may be ones formed over a singlecrystalline semiconductor substrate or may be circuits that are eachformed using a TFT over a glass substrate. In FIGS. 18A and 18B, eachdriver IC 2751 is connected to an FPC (flexible printed circuit) 2750.

Further, in the case where a TFT provided in a pixel is formed using asemiconductor having high crystallinity, a scan line driver circuit 3702may be formed over a substrate 3700 as shown in FIG. 171. In FIG. 17B, apixel portion 3701 which is connected to a signal line input terminal3704 is controlled by an external driver circuit similar to that in FIG.17A. In the case where a TFT provided in a pixel is formed using apolycrystalline (microcrystalline) semiconductor, a single crystallinesemiconductor, or the like with high mobility, a pixel portion 4701, ascan line driver circuit 4702, and a signal line driver circuit 4704 canbe formed over a substrate 4700 as shown in FIG. 17C.

In FIG. 19, a display panel can be formed in any mode as follows: as thestructure shown in FIG. 17A, only a pixel portion 901 is formed, and ascan line driver circuit 903 and a signal line driver circuit 902 aremounted by a TAB method as shown in FIG. 18B or by a COG method as shownin FIG. 18A; a TFT is formed, and a pixel portion 901 and a scan linedriver circuit 903 are formed over a substrate, and a signal line drivercircuit 902 is separately mounted as a driver IC as shown in FIG. 177B;a pixel portion 901, a signal line driver circuit 902, and a scan linedriver circuit 903 are formed over one substrate as shown in FIG. 17C;and the like.

In FIG. 19, as a structure of other external circuits, a video signalamplifier circuit 905 for amplifying a video signal among signalsreceived by a tuner 904, a video signal processing circuit 906 forconverting the signals outputted from the video signal amplifier circuit905 into chrominance signals corresponding to colors of red, green, andblue respectively, a control circuit 907 for converting the video signalso as to be inputted to a driver IC, and the like are provided on aninput side of the video signal. The control circuit 907 outputs signalsto both a scan line side and a signal line side. In the case of digitaldriving, a signal dividing circuit 908 may be provided on the signalline side and an input digital signal may be divided into m pieces to besupplied.

Among signals received by the tuner 904, an audio signal is transmittedto an audio signal amplifier circuit 909, and the output thereof issupplied to a speaker 913 through an audio signal processing circuit910. A control circuit 911 receives control information on a receivingstation (receiving frequency) or sound volume from an input portion 912and transmits the signal to the tuner 904 or the audio signal processingcircuit 910.

A television set can be completed by incorporating the display moduleinto a chassis as shown in FIGS. 20A and 20B. When a liquid crystaldisplay module is used as a display module, a liquid crystal televisionset can be manufactured. When an EL display module is used, an ELtelevision set can be manufactured. In FIG. 20A, a main screen 2003 isformed using the display module, and a speaker portion 2009, anoperation switch, and the like are provided as its accessory equipment.Thus, a television set can be completed by the present invention.

A display panel 2002 is incorporated in a chassis 2001. With the use ofa receiver 2005, in addition to reception of general TV broadcast,communication of information can also be performed in one way (from atransmitter to a receiver) or in two ways (between a transmitter and areceiver or between receivers) by connection to a wired or wirelesscommunication network through a modem 2004. The television set can beoperated by switches incorporated in the chassis or by a remote controldevice 2006 separated from the main body. A display portion 2007 thatdisplays information to be outputted may also be provided in this remotecontrol device.

In addition, in the television set, a structure for displaying achannel, sound volume, or the like may be provided by formation of asubscreen 2008 with a second display panel in addition to the mainscreen 2003. In this structure, the main screen 2003 and the subscreen2008 can be formed using a liquid crystal display panel of the presentinvention. Alternatively, the main screen 2003 may be formed using an ELdisplay panel superior in a viewing angle, and the subscreen 2008 may beformed using a liquid crystal display panel capable of displaying withlow power consumption. In order to prioritize low power consumption, astructure in which the main screen 2003 is formed using a liquid crystaldisplay panel, the subscreen 2008 is formed using an EL display panel,and the sub-screen is able to flash on and off may be employed. By thepresent invention, a highly reliable display device can be manufacturedeven with the use of such a large substrate, and many TFTs andelectronic components.

FIG. 20B shows a television set having a large display portion, forexample, 20 to 80-inch display portion, which includes a chassis 2010, adisplay portion 2011, a remote control device 2012 which is an operationportion, a speaker portion 2013, and the like. The present invention isapplied to manufacture of the display portion 2011. The television setshown in FIG. 20B is a wall-hanging type, and does not need a widespace.

It is necessary to say that the present invention is not limited to thetelevision set and is also applicable to various uses such as a monitorof a personal computer, or in particular, a display medium with a largearea, for example, an information display board at a train station, anairport, or the like, or an advertisement display board on the street.

This embodiment mode can be combined with any of Embodiment Modes 1 to11 as appropriate.

Embodiment Mode 13

Examples of electronic devices in accordance with the present inventionare as follows: a television device (also referred to as simply atelevision, or a television receiver), a camera such as a digital cameraor a digital video camera, a cellular telephone device (simply alsoreferred to as a cellular phone or a cell-phone), a portable informationterminal such as PDA, a portable game machine, a computer monitor, acomputer, a sound reproducing device such as a car audio system, animage reproducing device including a recording medium, such as ahome-use game machine, and the like. Further, the present invention canbe applied to various amusement machines each having a display device,such as a pachinko machine, a slot machine, a pinball machine, and alarge game machine. Specific examples of them are described withreference to FIGS. 21A to 21F.

A portable information terminal device shown in FIG. 21A includes a mainbody 9201, a display portion 9202, and the like. The display device ofthe present invention can be applied to the display portion 9202. As aresult, a high-performance portable information terminal device whichcan display a high-quality image with high visibility can be provided.

A digital video camera shown in FIG. 21B includes a display portion9701, a display portion 9702, and the like. The display device of thepresent invention can be applied to the display portion 9701. As aresult, a high-performance digital video camera which can display ahigh-quality image with high visibility can be provided.

A cellular phone shown in FIG. 21C includes a main body 9101, a displayportion 9102, and the like. The display device of the present inventioncan be applied to the display portion 9102. As a result, ahigh-performance cellular phone which can display a high-quality imagewith high visibility can be provided.

A portable television device shown in FIG. 21D includes a main body9301, a display portion 9302 and the like. The display device of thepresent invention can be applied to the display portion 9302. As aresult, a high-performance portable television device which can displaya high-quality image with high visibility can be provided. The displaydevice of the present invention can be applied to a wide range oftelevision devices ranging from a small-sized television device mountedon a portable terminal such as a cellular phone, a medium-sizedtelevision device which can be carried, to a large-sized (for example,40-inch or larger) television device.

A portable computer shown in FIG. 21E includes a main body 9401, adisplay portion 9402, and the like. The display device of the presentinvention can be applied to the display portion 9402. As a result, ahigh-performance portable computer which can display a high-qualityimage with high visibility can be provided.

A slot machine shown in FIG. 21F includes a main body 9501, a displayportion 9502, and the like. The display device of the present inventioncan be applied to the display portion 9502. As a result, ahigh-performance slot machine which can display a high-quality imagewith high visibility can be provided.

As described above, a high-performance electronic device which candisplay a high-quality image with high visibility can be provided byusing the display device of the present invention.

This embodiment mode can be combined with any of Embodiment Modes 1 to12 as appropriate.

This application is based on Japanese Patent Application serial no.2006-327787 filed with Japan Patent Office on Dec. 5, 2006, the entirecontents of which are hereby incorporated by reference.

EXPLANATION OF REFERENCE

50: electrode layer, 52: electroluminescent layer, 53: electrode layer,54: insulating layer, 60: electrode layer, 61: light-emitting material,62: electroluminescent layer, 63: electrode layer, 64: insulating layer,100: substrate, 107: gate insulating layer, 167: insulating film, 168:insulating film, 177: pyramidal projection, 178: terminal electrodelayer, 181: insulating film, 185: electrode layer, 186: insulatinglayer, 188: light-emitting layer, 189: electrode layer, 190:light-emitting element, 192: sealing material, 193: a filler, 194: FPC,195: sealing substrate, 196: anisotropic conductive layer, 199: wiringlayer, 201: separation region, 202: external terminal connection region,203: wiring region, 204: peripheral driver circuit region, 205:connection region, 206: pixel region, 207: peripheral driver circuitregion, 208: peripheral driver circuit region, 209: peripheral drivercircuit region, 232: external terminal connection region, 233: sealingregion, 234: peripheral driver circuit region, 236: pixel region, 245:thin film transistor, 265: thin film transistor, 275: thin filmtransistor, 285: thin film transistor, 332: lamp reflector, 352:backlight unit, 395: electrode layer, 396: electrode layer, 401: coldcathode fluorescent lamp, 410: display device, 450: display device, 451:pyramidal projection, 460: display device, 461: pyramidal projection,470: display device, 471: pyramidal projection, 480: display device,481: pyramidal projection, 486: film, 502: gate electrode layer, 504:semiconductor layer, 520: substrate, 521: transistor, 523: insulatinglayer 524: substrate, 526: gate insulating layer, 528: partition(insulating layer), 529: pyramidal projection, 530: light-emittingelement, 531: electrode layer, 532: electroluminescent layer, 533:electrode layer, 534: insulating layer, 538: substrate, 54 a: insulatinglayer, 54 b: insulating layer, 550: substrate, 551: transistor, 554:semiconductor layer, 556: polarizer, 557: insulating layer, 558: gateinsulating layer, 560: pixel electrode layer, 561: insulating layer,562: liquid crystal layer, 563: insulating layer, 564: conductive layer,565: colored layer, 567: pyramidal projection, 568: substrate, 569:polarizer, 581: transistor, 582: gate electrode layer, 584: gateinsulating layer, 586: semiconductor layer, 589: spherical particle,594: cavity, 595: filler, 596: substrate, 598: insulating layer, 600:substrate, 606: pixel region, 607: driver circuit region, 611:insulating film, 612: insulating film, 615: insulating film, 616:insulating film, 620: transistor, 621: transistor, 622: transistor, 623:capacitor, 630: pixel electrode layer, 631: insulating layer, 632:liquid crystal layer, 633: insulating layer, 634: conductive layer, 635:colored layer, 637: spacer, 641: polarizer, 642: pyramidal projection,643: polarizer (polarizing plate), 64 a: insulating layer, 64 b:insulating layer, 678: terminal electrode layer, 692: sealing material,695: counter substrate, 696: anisotropic conductive layer, 752:electroluminescent layer, 754: insulating layer, 757: pyramidalprojection, 758: substrate, 762: electroluminescent layer, 764:insulating layer, 765: partition (insulating layer), 768: protectivelater, 772: electroluminescent layer, 774: insulating layer, 775:partition (insulating layer), 776: insulating layer, 777: pyramidalprojection, 778: substrate, 792: electroluminescent layer, 794:insulating layer, 798: substrate, 802: third layer, 803: second layer,804: first layer, 850: electrode layer, 860: electroluminescent layer,870: electrode layer, 901: pixel portion, 902: signal line drivercircuit, 903: scan line driver circuit, 904: tuner, 905: video signalamplifier circuit, 906: video signal processing circuit, 907: controlcircuit, 908: signal dividing circuit, 909: audio signal amplifiercircuit, 910: audio signal processing circuit, 911: control circuit,912: input portion, 913: speaker, 101 a: base film, 101 b: base film,1300: element substrate, 1310: gate insulating layer, 1311: insulatingfilm, 1312: insulating film, 1314: insulating layer, 1317: electrodelayer, 1319: light-emitting layer, 1320: electrode layer, 1322: filler,1324: wiring layer, 1325: sealing substrate, 1327: pyramidal projection,1332: sealing material, 1333: wiring layer, 1355: thin film transistor,1365: thin film transistor, 1375: thin film transistor, 1381: terminalelectrode layer, 1382: anisotropic conductive layer, 1383: FPC, 1385:thin film transistor, 1600: element substrate, 1605: light-emittingelement, 1610: gate insulating layer, 1611: insulating film, 1612:insulating film, 1614: insulating layer, 1617: electrode layer, 1619:light-emitting layer, 1620: electrode layer, 1621: protective film,1622: filler, 1625: sealing substrate, 1632: sealing material, 1633:wiring layer, 1655: thin film transistor, 1665: thin film transistor,1675: thin film transistor, 1681: terminal electrode layer, 1682:anisotropic conductive layer, 1683: FPC, 1685: thin film transistor,1700: substrate, 1703: liquid crystal layer, 1704: insulating layer,1705: counter electrode layer, 1706: colored layer, 1710: substrate,1712: insulating layer, 1714: polarizing plate, 179 a: wiring, 179 b:wiring, 2001: chassis, 2002: display panel, 2003: main screen, 2004:modem, 2005: receiver, 2006: remote control device, 2007: displayportion, 2008: subscreen, 2009: speaker portion, 2010: chassis, 2011:display portion, 2012: remote control device, 2013: speaker portion,2600: TFT substrate, 2601: counter substrate, 2602: sealing material,2603: pixel portion, 2604: display element, 2605: colored layer, 2606:polarizing plate, 2607: polarizing plate, 2609: flexible wiring board,2610: cold cathode fluorescent lamp, 2611 reflective plate, 2612:circuit substrate, 2613: diffusing plate, 2626: pyramidal projection,2700: substrate, 2701: pixel portion, 2702: pixel, 2703: scan line inputterminal, 2704: signal line input terminal, 2751: driver IC, 2800:substrate, 2801: protective circuit portion, 2802: TFT, 2803: TFT, 2804:light-emitting element, 2805: light-emitting element, 2809: drivercircuit, 2810: wiring substrate, 2811: external circuit substrate, 2812:heat sink, 2813: heat pipe, 2820: sealing substrate, 2827: pyramidalprojection, 2912: control portion, 3700: substrate, 3701: pixel portion,3702: scan line driver circuit, 3704: signal line input terminal 411 a:pyramidal projection, 411 b: pyramidal projection, 411 c: pyramidalprojection, 412 a: incident light ray from external 412 b: reflectedlight ray, 412 c: reflected light ray, 412 d: reflected light ray, 413a: transmitted light ray, 413 b: transmitted light ray, 413 c:transmitted light ray, 413 d: transmitted light ray, 4700: substrate,4701: pixel portion, 4702: scan line driver circuit, 4704: signal linedriver circuit, 5000: pyramidal projection, 503 a: semiconductor layer,5100: top, 5200: pyramidal projection, 5230: pyramidal projection, 5250:pyramidal projection, 525 a: wiring layer, 525 b: wiring layer, 552 a:gate electrode layer, 553 a: semiconductor layer, 555 a: wiring layer,585 a: wiring layer, 585 b: wiring layer, 587 a: electrode layer, 587 b:electrode layer, 590 a: black region, 590 b: white region, 604 a: basefilm, 604 b: base film, 608 a: driver circuit region, 608 b: drivercircuit region, 751 a: electrode layer, 751 b: electrode layer, 751 c:electrode layer, 753 a: electrode layer, 753 b: electrode layer, 753 c:electrode layer, 761 a: electrode layer, 761 b: electrode layer, 761 c:electrode layer, 763 b: electrode layer, 771 a: electrode layer, 771 b:electrode layer, 771 c: electrode layer, 773 b: electrode layer, 791 a:electrode layer, 791 b: electrode layer, 791 c: electrode layer, 793 b:electrode layer, 9101: main body, 9102: display portion, 9201: mainbody, 9202: display portion, 9301: main body, 9302: display portion,9404: main body, 9402: display portion, 9701: display portion, 9702:display portion, 1301 a: insulating film, 1301 b: insulating film, 1601a: insulating film, 1601 b: insulating film, 1627 a: pyramidalprojection, 1701 a: pixel electrode layer, 2806 a: spacer, 2806 b:spacer, 2807 a: colored layer, 2807 b: colored layer, 2807 c: coloredlayer, 2910 a: red light source 2910 b: green light source, 2910 c: bluelight source, 5001 a: pyramidal projection, 520 a: pyramidal projection,5231 a: pyramidal projection, 5251 a: pyramidal projection

1. An antireflective film comprising: a plurality of pyramidalprojections, wherein tops of the plurality of pyramidal projections areevenly spaced; and wherein each side of the base of one pyramidalprojection is in contact with one side of the base of an adjacentpyramidal projection.
 2. The antireflective film according to claim 1,wherein six adjacent pyramidal projections are arranged around onepyramidal projection.
 3. An antireflective film comprising: a pluralityof pyramidal projections, wherein tops of the plurality of pyramidalprojections are evenly spaced; wherein each side of the base of onepyramidal projection is in contact with one side of the base of anadjacent pyramidal projection; and wherein the distance between the topsof the plurality of pyramidal projections is equal to or shorter than350 nm and the height of each of the plurality of pyramidal projectionsis equal to or longer than 800 nm.
 4. The antireflective film accordingto claim 3, wherein six adjacent pyramidal projections are arrangedaround one pyramidal projection.
 5. The antireflective film according toclaim 3, wherein the fill rate of bases of the plurality of pyramidalprojections per unit area is equal to or more than 80%.
 6. Theantireflective film according to claim 4, wherein the fill rate of basesof the plurality of pyramidal projections per unit area is equal to ormore than 80%.
 7. The antireflective film according to claim 5, whereinthe ratio of the height of a pyramidal projection to the width of a basethereof is equal to or more than
 5. 8. The antireflective film accordingto claim 6, wherein the ratio of the height of a pyramidal projection tothe width of a base thereof is equal to or more than
 5. 9. A displaydevice comprising: a pair of substrates at least one of which is alight-transmitting substrate; a display element provided between thepair of substrates; and a plurality of pyramidal projections on an outerside of the light-transmitting substrate, wherein tops of the pluralityof pyramidal projections are evenly spaced; and wherein each side of thebase of one pyramidal projection is in contact with one side of the baseof an adjacent pyramidal projection.
 10. The display device according toclaim 9, wherein six adjacent pyramidal projections are arranged aroundone pyramidal projection.
 11. A display device comprising: a pair ofsubstrates at least one of which is a light-transmitting substrate; adisplay element provided between the pair of substrates; and a pluralityof pyramidal projections on an outer side of the light-transmittingsubstrate, wherein tops of the plurality of pyramidal projections areevenly spaced; wherein each side of the base of one pyramidal projectionis in contact with one side of the base of an adjacent pyramidalprojection; and wherein the distance between the tops of the pluralityof pyramidal projections is equal to or shorter than 350 nm and theheight of each of the plurality of pyramidal projections is equal to orlonger than 800 nm.
 12. The display device according to claim 11,wherein six adjacent pyramidal projections are arranged around onepyramidal projection.
 13. The display device according to claim 11,wherein the fill rate of bases of the plurality of pyramidal projectionsper unit area is equal to or more than 80%.
 14. The display deviceaccording to claim 12, wherein the fill rate of bases of the pluralityof pyramidal projections per unit area is equal to or more than 80%. 15.The display device according to claim 13, wherein the ratio of theheight of a pyramidal projection to the width of a base there of isequal to or more than
 5. 16. The display device according to claim 14,wherein the ratio of the height of a pyramidal projection to the widthof a base there of is equal to or more than
 5. 17. The display deviceaccording to claim 9, wherein a polarizing plate is provided between thelight-transmitting substrate and the plurality of pyramidal projections.18. The display device according to claim 9, wherein the display elementis a light-emitting element.
 19. The display device according to claim9, wherein the display element is a liquid crystal display element. 20.The display device according to claim 11, wherein a polarizing plate isprovided between the light-transmitting substrate and the plurality ofpyramidal projections.
 21. The display device according to claim 11,wherein the display element is a light-emitting element.
 22. The displaydevice according to claim 11, wherein the display element is a liquidcrystal display element.